A rapid method for constructing and evaluating VOC source component spectra.

Abstract

This invention relates to a rapid method for constructing and evaluating VOCs source composition profiles, comprising the following steps: Step S1: On-site investigation to determine the target VOCs emission source, sampling port location, and sampling method; Step S2: On-site collection of target VOCs source samples using gas bags or Summa canisters; Step S3: Within 1-2 hours of collection, the samples are transported to a vehicle-mounted online VOCs analysis laboratory located near the sampling source for analysis and measurement using analytical instruments; Step S4: Based on the measured data from multiple VOCs samples of the same type of emission source, the VOCs source composition profile of that source type is constructed and evaluated. This invention employs an on-site sampling and analysis method, improving the rationality of the on-site sampling method and the dilution scheme for high-concentration VOCs source samples to bring them within the detection range of the analytical instruments, thereby improving the timeliness and accuracy of data acquisition.

Description

Technical Field

[0001] This invention relates to the field of air pollution control, and in particular to a rapid method for constructing and evaluating VOCs source composition profiles. Background Technology

[0002] Volatile organic compounds (VOCs) are key precursors to ozone formation, and studies have shown that most urban or regional ozone pollution occurs within VOCs control zones. Therefore, research on the characteristics and source apportionment of environmental VOCs pollution plays a crucial role in the effective prevention and control of atmospheric ozone pollution.

[0003] Receptor models are the mainstream technique for VOCs source apportionment in the environment. Commonly used receptor models include positive definite matrix factorization (PMF) and chemical mass balance (CMB) models. PMF models require relevant source component spectral information to assign clear physical meaning to factors during factor identification, while CMB models require local source component spectra as computational data. Therefore, VOCs source component spectra play a crucial and irreplaceable role in their source apportionment.

[0004] The current mainstream method or process for constructing VOCs source composition profiles mainly involves first sampling on-site using gas bags or SUMMA tanks, then transporting the samples to the laboratory for VOCs species analysis and measurement, and finally constructing the source composition profile using mathematical or statistical methods. However, two key problems remain unresolved: first, the traditional "VOCs source sample collection - laboratory analysis and measurement - source composition profile construction" method is time-consuming, often requiring at least two weeks or even more than a month; second, during the long period from on-site sample collection to laboratory analysis, VOCs species undergo significant chemical transformations, making it difficult for the constructed source composition profile to accurately characterize the actual emission characteristics of typical VOCs sources.

[0005] Therefore, rapidly and effectively constructing source composition spectra that can accurately characterize VOC emission sources can better support the practical application of VOC source apportionment methods, thereby more effectively supporting the prevention and control of atmospheric ozone pollution. Summary of the Invention

[0006] The purpose of this invention is to propose a source composition profile construction and evaluation method that can rapidly and accurately characterize the emission features of volatile organic compounds (VOCs), reduce the impact of chemical reaction transformation or loss of VOC species, significantly improve the timeliness and accuracy of VOCs source composition profile construction, thereby enhancing the accuracy of environmental VOCs source apportionment results, and aiming to more effectively support the prevention and control of atmospheric ozone pollution.

[0007] To achieve the above objectives, this invention provides a rapid method for constructing and evaluating VOCs source component spectra, comprising the following steps:

[0008] Step S1: Conduct on-site investigation to determine the target VOCs emission sources (such as industrial enterprises, coal-fired power plants, motor vehicles, catering sources, etc.), sampling port locations, and sampling methods;

[0009] Step S2: Collect target VOCs source samples on-site using air bags or Summa canisters;

[0010] Step S3: The sample is sent to a vehicle-mounted VOCs online analysis laboratory located near the sampling source within 1 to 2 hours after collection, and analyzed and measured using analytical instruments;

[0011] The vehicle-mounted VOCs online analysis laboratory includes a dilution system and an analysis system. The dilution system uses high-purity nitrogen to dilute the concentration of the source sample to the detection range of the analysis instrument. A handheld gas detector is used to measure the total VOCs concentration at the sampling port, and the specific dilution factor is calculated by combining the source emission VOCs concentration with the detection limit of the analysis instrument. The analysis system connects the diluted source sample to the VOCs analysis instrument via an inert tubing for analysis.

[0012] Step S4: Based on the measured VOCs sample data from multiple emission sources of the same type, construct and evaluate the source composition profile of VOCs of this type.

[0013] Specifically, the geometric arithmetic mean method was used to construct the source component spectra, and at least three or more samples of the same type of target source were collected; the divergence coefficient method was used to evaluate the differences and similarities of the source component spectra.

[0014] Preferably, in step S1, the steps of determining the target VOCs emission sources (such as industrial enterprises, coal-fired power plants, motor vehicles, catering sources, etc.), sampling port locations, and sampling methods through on-site investigation include:

[0015] Collect and organize environmental statistics data, pollution source emission inventories, and pollution census data for the target area; select typical VOCs emission sources for on-site investigation to obtain basic information, pollution removal facilities, and pollutant emission information of key VOCs emission sources in the target area; and determine typical target sampling sources and their sampling port locations that can represent the target area based on the investigation results.

[0016] Preferably, the steps for on-site collection of target VOCs source samples using air bags include:

[0017] Step S211: Before sampling, place the gas bag directly into the vacuum sampling box, connect the valve on the gas bag to the gas supply line in the sampling box, and close and seal the sampling vacuum box;

[0018] Step S212: For industrial enterprises, coal-fired power plants, and catering sources, insert the heated sampler (including the front-end smoke gun and the rear-end heated sampling tube) into the sampling port of the end exhaust chimney of the target source, so that the front end of the sampler smoke gun is close to the center area of ​​the chimney pipe, or the front end of the heated sampler smoke gun is directly extended to the middle of the exhaust chimney opening (i.e., the emission outlet) of the target source; for motor vehicles, extend the front end of the heated sampler smoke gun directly to the position close to the exhaust outlet of the motor vehicle; if the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, activate the heating of the sampling tube to make it consistent with the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle.

[0019] Step S213: Connect the end of the heated sampler to the air inlet of the vacuum sampling box using a polytetrafluoroethylene connecting tube; start the vacuum pump in the vacuum sampling box to maintain a negative pressure inside the sampling box, so that the gas bag begins to collect waste gas samples; when the sampling volume in the gas bag reaches 75%~85% of the maximum volume of the gas bag, turn off the vacuum pump and end the sampling.

[0020] Step S214: Quickly open the vacuum sampling box, close the gas bag valve, remove the sampling gas bag, and place it in a light-proof container; then quickly transfer it to the vehicle-mounted VOCs online analysis laboratory for analysis and measurement.

[0021] Preferably, the steps for on-site collection of target VOCs source samples using a Summa canister include:

[0022] Step S221: Before sampling, use a fully automated cleaning device to clean the SUMMA canisters; after cleaning, vacuum the SUMMA canisters and set them aside for use; for every 20 SUMMA canisters cleaned, at least one canister should be injected with high-purity nitrogen for analysis to determine whether the cleaning process is clean; after cleaning, the SUMMA canisters that have been used for source sample collection should be analyzed for background contaminants before the next use to ensure that they are clean.

[0023] Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuum-evacuated SUMMA canister is brought to the sampling point; the end of the heated sampler (see step S212 for details) is connected to the air inlet of the SUMMA canister (a particulate matter and water vapor filter is installed at the front end of the air inlet); for industrial enterprises, coal-fired power plants, and catering sources, the front end of the heated sampler is inserted into the sampling port of the end exhaust chimney of the target enterprise, so that the front end of the sampler is close to the center area of ​​the chimney pipe, or the front end of the heated sampler is directly inserted to the middle of the exhaust chimney opening (i.e., the emission outlet) of the target source; for motor vehicles, the front end of the heated sampler is directly inserted to the position near the exhaust outlet of the motor vehicle; if the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is activated to make it consistent with the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the SUMMA canister is opened to start collecting exhaust gas samples, and after the pressure inside the canister is consistent with the sampling environment pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

[0024] Preferably, the high-concentration source sample after collection is sent to the dilution system in the vehicle-mounted laboratory for dilution. The dilution factor or ratio is mainly derived from the conversion between the source emission VOCs concentration measured by the handheld gas detector and the measurement range of the vehicle-mounted online VOCs analyzer. The concentration of the diluted source sample must meet the detection range of the online VOCs analyzer.

[0025] The dilution system includes: a dilution tank, an air inlet, an air outlet, and a high-purity nitrogen cylinder;

[0026] The dilution tank is the main body of the dilution system. It can simultaneously introduce a source sample waste gas and high-purity nitrogen gas of a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed.

[0027] The dilution chamber has two air inlets: a sample gas inlet and a high-purity nitrogen inlet. The sample gas inlet is connected to the source sampling gas bag, and the nitrogen inlet is connected to the high-purity nitrogen cylinder via a rubber tube.

[0028] One outlet of the dilution chamber: connects to the gas bags of samples diluted with different volume ratios.

[0029] Preferably, after connecting the sample gas and high-purity nitrogen to the dilution system, the inlet ratio of high-concentration source sample gas to high-purity nitrogen (i.e., the dilution ratio) is set in the software operation interface of the dilution system. Before each injection, the inlet and outlet pipelines need to be purged with high-purity nitrogen for 10 seconds to eliminate interference from residual samples in the pipelines. The diluted and mixed sample gas enters a new clean gas bag through the outlet. When the sampling volume in the new gas bag reaches 75% to 85% of the maximum volume of the gas bag, the dilution process ends. The diluted sample gas bag is then connected to the inlet of the analyzer to perform the analysis and determination of VOCs species volume concentration (unit: ppbv).

[0030] Preferably, constructing the source component spectrum using the geometric arithmetic mean method includes:

[0031] First, the VOCs species volume concentration (ppbv) was determined based on the analysis of the diluted sample, and then converted to mass concentration (μg / m³) using the following formula. 3 )data:

[0032]

[0033] In the formula: C Q The mass concentration of VOC species, in μg / m³ 3 C V ppbv represents volume concentration or volume mixing ratio; M represents molecular weight; V represents volume concentration or volume mixing ratio. m The value is the molar volume of the gas, in g / mol, which is 22.4 L / mol under standard conditions (i.e., air temperature of 273.15ºK and air pressure of 1013.25hPa).

[0034] Then, calculate the proportion of the mass concentration of all measured VOC species to the total mass concentration (i.e., the sum of the mass concentrations of all measured VOC species), which is the mass percentage (in %). The data for each source sample is the mass percentage (%) of all measured VOC species in that sample.

[0035] Finally, source sample data (at least 3 samples) from the same source class were analyzed and a source component spectrum (including mean and standard deviation) was constructed using the geometric arithmetic mean method. The formula for calculating the average content of VOC species in the source component spectrum is as follows:

[0036]

[0037] In the formula: Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; This represents the number of source samples.

[0038] The formula for calculating the standard deviation of VOC species content in the source component spectrum is as follows:

[0039]

[0040] In the formula: Species in a certain type of source spectrum to be constructed Standard deviation of content, % Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; This represents the number of source samples.

[0041] Preferably, the divergence coefficient (CD) method is used to assess the differences in the component spectra of different VOCs sources, and the formula for calculating CD is as follows:

[0042]

[0043] In the formula: To compare the first table Class source component spectrum and the first The divergence coefficient defined in the source component spectrum; To include the number of species in the calculation, the number of individuals is [number missing]. For the first In the class component spectrum, the first The quality fraction of each species, %

[0044] If CD approaches 0, it indicates that the source component spectra are more similar; when CD ≥ 0.4, it indicates that the source component spectra are significantly different; when 0.2 ≤ CD < 0.4, the source component spectra are similar; when CD < 0.2, the source component spectra are somewhat similar.

[0045] Based on the above technical solution, the advantages of the present invention are:

[0046] This invention significantly improves the timeliness of VOCs source component profile construction, reducing the time from source sample collection to profile establishment to within 12 hours. This significantly enhances the accuracy and representativeness of VOCs source component profiles, avoiding the influence of chemical reaction transformations of VOCs species during source sample collection and analysis, thus enabling more accurate VOCs source component profile construction. Furthermore, this invention eliminates the complex process of transporting source samples from the field to the laboratory for analysis, reducing transportation and analysis costs. Attached Figure Description

[0047] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0048] Figure 1 A flowchart illustrating the steps of a rapid method for constructing and evaluating VOC source composition profiles;

[0049] Figure 2 A diagram illustrating the steps for on-site collection of target VOCs source samples using air bags;

[0050] Figure 3 A diagram illustrating the steps for on-site collection of target VOCs source samples using a Summa canister.

[0051] Figure 4 A flowchart outlining a rapid method for constructing and evaluating VOC source component profiles;

[0052] Figure 5 This is a flowchart of the sample dilution process;

[0053] Figure 6 Example of a field survey of VOCs emission sources;

[0054] Figure 7 This is a schematic diagram of the operation of the continuous atmospheric volatile organic compound monitoring system in an embodiment of the present invention;

[0055] Figure 8 The solvent constructed in this embodiment of the invention uses VOCs source component profiles of relevant source classes;

[0056] Figure 9 The solvent VOC source component spectra constructed in the embodiments of the present invention are source component spectra of the automobile manufacturing industry, electric vehicle manufacturing industry, plastic product manufacturing industry, footwear industry, and packaging and printing industry. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0058] This invention provides a rapid method for constructing and evaluating VOC source component spectra, such as... Figure 1 , Figure 4 As shown, it includes the following steps:

[0059] Step S1: Conduct on-site investigation to determine the target VOCs emission sources (such as industrial enterprises, coal-fired power plants, motor vehicles, catering sources, etc.), sampling port locations, and sampling methods.

[0060] Specifically, on-site investigation to determine the target VOCs emission sources, sampling port locations, and sampling methods includes: collecting and sorting out basic data such as environmental statistics data, pollution source emission inventories, and pollution census data for the target area; selecting typical VOCs emission sources for on-site investigation; and obtaining basic information on key VOCs emission sources, pollution removal facilities, and pollutant emission information for the target area. Figure 6 A preferred on-site survey form for VOCs emission sources from industrial or coal-fired power plants is presented. Based on the survey results, typical target sampling sources and their sampling port locations that can represent the target area are identified.

[0061] Step S2: Collect target VOCs source samples on-site using air bags or SUMMA canisters.

[0062] Among them, such as Figure 2 As shown, the steps for on-site collection of target VOCs source samples using air bags include:

[0063] Step S211: Before sampling, place the gas bag in the vacuum sampling box, connect the valve on the gas bag to the gas supply line in the sampling box, and close and seal the sampling vacuum box;

[0064] Step S212: For industrial enterprises, coal-fired power plants, and catering sources, insert the heated sampler (including the front-end smoke gun and the rear-end heated sampling tube) into the sampling port of the target enterprise's end exhaust chimney, so that the front end of the sampler smoke gun is close to the center area of ​​the chimney pipe, or the front end of the heated sampler smoke gun is directly extended to the middle of the exhaust chimney opening (i.e., the emission outlet) of the target source; for motor vehicles, extend the front end of the heated sampler smoke gun directly to the position near the vehicle exhaust outlet; if the exhaust gas temperature inside the chimney or the vehicle exhaust temperature is higher than the ambient temperature, activate the heating of the sampling tube to make it consistent with the exhaust gas temperature inside the chimney or the vehicle exhaust temperature.

[0065] Step S213: Connect the end of the heated sampler to the air inlet of the vacuum sampling box using a PTFE connecting tube; start the vacuum pump in the vacuum sampling box to maintain a negative pressure inside the sampling box, so that the gas bag begins to collect waste gas samples; when the sampling volume in the gas bag reaches 75%~85% of the maximum volume of the gas bag, turn off the vacuum pump and end the sampling.

[0066] Step S214: Quickly open the vacuum sampling box, close the gas bag valve, remove the sampling gas bag, and place it in a light-proof container; then quickly transfer it to the vehicle-mounted VOCs online analysis laboratory for analysis and measurement.

[0067] Among them, such as Figure 3 As shown, the steps for on-site collection of target VOCs source samples using a Summa canister include:

[0068] Step S221: Before sampling, use a fully automated canister cleaning device to clean the SUMMA canisters; after cleaning, vacuum the SUMMA canisters and set them aside for use; for every 20 SUMMA canisters cleaned, at least one canister should be injected with high-purity nitrogen for analysis to determine whether the cleaning process is clean; after cleaning, the SUMMA canisters that have been used for source sample collection should be analyzed for background contaminants before the next use to ensure that they are clean.

[0069] Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuum-evacuated SUMMA canister is brought to the sampling point; the end of the heated sampler (see step S212 for details) is connected to the air inlet of the SUMMA canister (a particulate matter and water vapor filter is installed at the front end of the air inlet); for industrial enterprises, coal-fired power plants, and catering sources, the front end of the heated sampler is inserted into the sampling port of the end exhaust chimney of the target enterprise, so that the front end of the sampler is close to the center area of ​​the chimney pipe, or the front end of the heated sampler is directly inserted to the middle of the exhaust chimney opening (i.e., the emission outlet) of the target source; for motor vehicles, the front end of the heated sampler is directly inserted to the position near the exhaust outlet of the motor vehicle; if the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is activated to make it consistent with the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the SUMMA canister is opened to start collecting exhaust gas samples, and after the pressure inside the canister is consistent with the sampling environment pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

[0070] It should be noted that quality control during the sampling process includes: using properly cleaned Summa canisters for sample collection; positioning the front end of the sampler nozzle close to the center of the chimney duct or the middle of the target source's exhaust outlet; and keeping the sampling tube as short as possible.

[0071] Step S3: The sample is sent to a vehicle-mounted VOCs online analysis laboratory located near the sampling source within 1 to 2 hours after collection, and analyzed and measured using analytical instruments.

[0072] The vehicle-mounted VOCs online analysis laboratory includes a dilution system and an analysis system. The dilution system uses high-purity nitrogen to dilute the concentration of the source sample to the detection range of the analysis instrument. A handheld gas detector is used to measure the total VOCs concentration at the sampling port, and the specific dilution factor is calculated by combining the source emission VOCs concentration with the detection limit of the vehicle-mounted VOCs analyzer. The diluted and mixed sample gas enters a new clean gas bag through the gas outlet. The dilution process ends when the sampling volume in the new gas bag reaches 75% to 85% of the maximum volume of the gas bag. The diluted sample gas bag is then connected to the inlet of the analysis instrument.

[0073] Each sample was placed in a light-proof container after collection and transported to the mobile VOCs online analysis laboratory within 1-2 hours for timely analysis to avoid chemical consumption of reactive VOCs. The mobile laboratory mainly includes a dilution system and an analysis system. The specific measurement process is as follows:

[0074] Preferably, the high-concentration source sample after collection is diluted using a dilution system. The dilution factor or ratio is mainly derived from the conversion between the total concentration of VOCs emitted from the source measured by a handheld gas detector (such as the ZR-3110 portable gas detector, which uses a PID detector) and the measurement range of the vehicle-mounted online VOCs analyzer. The concentration of the diluted source sample must meet the detection range of the online VOCs analyzer.

[0075] Furthermore, such as Figure 5 As shown, the dilution system includes: a dilution tank, an air inlet, an air outlet, and a high-purity nitrogen cylinder;

[0076] The dilution tank is the main body of the dilution system. It can simultaneously introduce a source sample waste gas and high-purity nitrogen gas of a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed.

[0077] The dilution chamber has two air inlets: a sample gas inlet and a pure nitrogen inlet. The sample gas inlet is connected to the source sampling gas bag, and the nitrogen inlet is connected to a high-purity nitrogen cylinder via a rubber tube.

[0078] One outlet of the dilution chamber: connects to the gas bags of samples diluted with different volume ratios.

[0079] Preferably, after connecting the sample gas and high-purity nitrogen to the dilution system, the inlet ratio of high-concentration source sample gas to high-purity nitrogen (i.e., the dilution ratio) is set in the software operation interface of the dilution system. Before each injection, the inlet and outlet pipelines need to be purged with high-purity nitrogen for 10 seconds to eliminate interference from residual samples in the pipelines. The diluted and mixed sample gas enters a new clean gas bag through the outlet. When the sampling volume in the new gas bag reaches 75% to 85% of the maximum volume of the gas bag, the dilution process ends. The diluted sample gas bag is then connected to the inlet of the analyzer to perform the analysis and determination of VOCs species volume concentration (unit: ppbv).

[0080] Sample analysis and determination: The diluted sample gas bag is connected to the analytical instrument via an inert tubing for analysis. The analytical instrument can be a common online VOCs analyzer such as GC-MS / FID, which can analyze at least 100 VOCs species (covering alkanes, alkenes, aromatic hydrocarbons, alkynes, halogenated hydrocarbons and oxygen-containing VOCs, etc.).

[0081] Step S4: Based on the measured VOCs sample data from multiple emission sources of the same type, construct and evaluate the VOCs source composition profile for this type of source.

[0082] Preferably, constructing the source component spectrum using the geometric arithmetic mean method includes:

[0083] First, the VOCs species volume concentration (ppbv) was determined based on the analysis of the diluted sample, and then converted to mass concentration (μg / m³) using the following formula. 3 )data:

[0084]

[0085] In the formula: C Q The mass concentration of VOC species, in μg / m³ 3 C V ppbv represents volume concentration or volume mixing ratio; M represents molecular weight; V represents volume concentration or volume mixing ratio. m The value is the molar volume of the gas, in g / mol, which is 22.4 L / mol under standard conditions (i.e., air temperature of 273.15ºK and air pressure of 1013.25hPa).

[0086] Then, calculate the proportion of the mass concentration of all measured VOC species to the total mass concentration (i.e., the sum of the mass concentrations of all measured VOC species), which is the mass percentage (in %). The data for each source sample is the mass percentage (%) of all measured VOC species in that sample.

[0087] Finally, source sample data (at least 3 samples) from the same source class were analyzed, and the geometric arithmetic mean method was used to construct the source component spectrum (including mean and standard deviation) for that source class. The formula for calculating the average content of VOC species in the source component spectrum is as follows:

[0088]

[0089] In the formula: Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; This represents the number of source samples.

[0090] The formula for calculating the standard deviation of VOC species content in the source component spectrum is as follows:

[0091]

[0092] In the formula: Species in a certain type of source spectrum to be constructed Standard deviation of content, % Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; This represents the number of source samples.

[0093] Preferably, the divergence coefficient (CD) method is used to assess the differences and similarities in the component spectra of non-VOCs sources. The calculation formula for the CD method is as follows:

[0094]

[0095] In the formula: To compare the first table Class source component spectrum and the first The divergence coefficient defined in the source component spectrum; To include the number of species in the calculation, the number of individuals is [number missing]. For the first In the class component spectrum, the first The quality fraction of each species, %

[0096] If CD approaches 0, it indicates that the component spectra are more similar; when CD ≥ 0.4, it indicates that the differences between the source component spectra are relatively large; when 0.2 ≤ CD < 0.4, the source component spectra are similar; when CD < 0.2, the source component spectra are somewhat similar.

[0097] This invention employs an on-site sampling and analysis method. By improving the rationality of the on-site sampling method and the dilution scheme for high-concentration VOCs samples, the samples are brought within the detection range of the analytical instrument, thereby improving the timeliness and accuracy of the data obtained.

[0098] To further illustrate the technical solution and detailed process of this invention, this embodiment takes an application in Zhumadian City, Henan Province as an example. VOCs samples from typical solvent-using industries were collected and rapidly analyzed using a vehicle-mounted online VOCs analysis laboratory. VOCs source composition profiles for different solvent-using industries were constructed and evaluated. The specific implementation process is as follows:

[0099] (1) On-site investigation to determine the VOCs emitting enterprises related to solvent use, the location of sampling ports and sampling methods.

[0100] Basic data such as environmental statistics, pollution source emission inventories, and pollution source census data of Zhumadian were collected. On-site investigations were conducted on relevant VOCs-emitting enterprises using solvents to determine the basic information, pollution control facilities, and pollutant emission status of key emitting enterprises in Zhumadian City. Specifically, as follows... Figure 6 The table shows the on-site survey results of VOCs emission sources in China.

[0101] Based on the results of the on-site survey, this embodiment selected VOCs emitting enterprises related to solvent use sources. Samples were collected from the chimney outlets of the enterprises' production workshops using gas bags under normal production conditions. The selection of sampling locations, sampling frequency, and sampling time for each enterprise, as well as related operations, complied with relevant industry standards.

[0102] (2) Use gas bags to collect on-site samples of solvent-related VOCs sources.

[0103] The gas bag has a volume of 3L and is made of polytetrafluoroethylene (PTFE). The vacuum chamber uses the ZR-3730 type pollution source vacuum chamber gas bag sampler.

[0104] Air bag sampling process:

[0105] ① Before sampling, place the gas bag directly into the vacuum sampling box, connect the valve on the gas bag to the gas supply line in the sampling box, and close and seal the sampling vacuum box;

[0106] ② Insert the heated sampler (including the front smoke gun and the rear heated sampling tube) into the middle of the exhaust chimney (i.e., the exhaust outlet) of the solvent-using enterprise; if the exhaust gas temperature of the chimney is higher than the ambient temperature, start the heating of the sampling tube to make it consistent with the exhaust gas temperature of the chimney.

[0107] ③Use a PTFE connecting tube to connect the end of the heated sampler to the air inlet of the vacuum sampling box; start the vacuum pump in the vacuum sampling box to maintain a negative pressure state inside the sampling box, so that the gas bag begins to collect waste gas samples; when the sampling volume in the gas bag reaches 75%~85% of the maximum volume of the gas bag, turn off the vacuum pump and end the sampling.

[0108] ④ Quickly open the vacuum sampling box, close the gas bag valve, take out the sampling gas bag, and put it into a light-proof container; then quickly transfer it to the vehicle-mounted VOCs online analysis laboratory parked in the factory area for analysis and measurement.

[0109] ⑤ Measure and record the exhaust gas temperature, exhaust gas flow rate, and moisture content in the exhaust pipe, and follow the relevant industry standards for operation procedures.

[0110] ⑥ Record the sample number, operating conditions during sample collection, ambient temperature, atmospheric pressure, sampling time, and other relevant information. Other related records shall comply with the provisions of relevant industry standards.

[0111] Quality control methods during gas bag sampling: Use new gas bags when collecting samples; position the front end of the sampler nozzle close to the middle of the chimney exhaust port; and keep the sampling tube as short as possible.

[0112] (3) The samples were sent to the vehicle-mounted VOCs online analysis laboratory for analysis within 1 to 2 hours after collection.

[0113] Each sample was placed in a light-proof container after collection and transported to a vehicle-mounted online VOCs analysis laboratory parked near the sampling source within 1-2 hours for analysis to avoid the reaction and consumption of VOCs species. The vehicle-mounted online VOCs analysis laboratory is mobile and can move synchronously with changes in the sampling location, allowing samples to be immediately sent in for analysis after collection. The vehicle-mounted online VOCs analysis laboratory used in this embodiment is equipped with a WHB high-precision dilution system and a ZF-PKU-VOC1007 atmospheric volatile organic compound continuous monitoring and analysis instrument, capable of performing sample dilution and VOCs species concentration analysis.

[0114] (3.1) Sample dilution

[0115] The high-concentration source samples collected are diluted using a dilution system. The dilution factor or ratio is mainly derived from the conversion between the total VOCs concentration of the source emissions measured by the ZR-3110 portable gas detector and the measurement range of the vehicle-mounted online VOCs analyzer. The concentration of the diluted source sample must meet the detection range of the online VOCs analyzer.

[0116] The dilution system includes: a dilution tank, an air inlet, an air outlet, and a high-purity nitrogen cylinder;

[0117] The dilution tank is the main body of the dilution system. It can simultaneously introduce a source sample waste gas and high-purity nitrogen gas of a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed.

[0118] The dilution chamber has two air inlets: a sample gas inlet and a pure nitrogen inlet. The sample gas inlet is connected to the source sampling gas bag, and the nitrogen inlet is connected to a high-purity nitrogen cylinder via a rubber tube.

[0119] One outlet of the dilution chamber: connects to the gas bags of samples diluted with different volume ratios.

[0120] After connecting the sample gas and high-purity nitrogen to the dilution system, set the inlet ratio of high-concentration source sample gas to high-purity nitrogen (i.e., the dilution ratio) in the software interface of the dilution system. Before each injection, the inlet and outlet pipelines need to be purged with high-purity nitrogen for 10 seconds to eliminate interference from residual samples in the pipelines. The diluted and mixed sample gas enters a new clean gas bag through the outlet. When the sampling volume in the new gas bag reaches 75% to 85% of the maximum volume of the gas bag, the dilution process ends.

[0121] (3.2) Sample Analysis

[0122] The diluted sample gas bag was connected to the analytical instrument via an inert tubing for analysis. The sample analysis was performed using a ZF-PKU-VOC1007 GC-MS / FID instrument for continuous atmospheric volatile organic compound monitoring. Figure 7 The diagram shows the working schematic of the ZF-PKU-VOC1007 atmospheric volatile organic compound continuous monitoring system. The system enriches samples by ultra-low temperature in an empty tube and performs qualitative and quantitative analysis of VOC species components using gas chromatography-mass spectrometry.

[0123] The quality control methods during the analysis and determination process should refer to the "Determination of Volatile Organic Compounds in Ambient Air by Canister Sampling / Gas Chromatography-Mass Spectrometry" (HJ 759-2015) and "Technical Requirements and Detection Methods for Continuous Gas Chromatography Monitoring Systems for Volatile Organic Compounds in Ambient Air" (HJ 1010-2018), and should include at least the following:

[0124] 1) Zero-point noise test: The zero-point noise of all 115 VOCs must be less than 0.05 ppb;

[0125] 2) Multi-point calibration: Introduce 115 standard gases with concentrations of 0.5, 2.0, 4.0, 6.0, 8.0, and 10.0 ppb, requiring the generation of the VOCs curve equation R for all 115 gases. 2 ≥0.95;

[0126] 3) Detection limit test: The detection limits of all 115 VOCs were ≤ 0.1 ppb;

[0127] 4) Accuracy and precision testing;

[0128] 5) Retention time precision test;

[0129] 6) Zero gas test: Using high-purity nitrogen as the zero gas (blank sample), the concentrations of all 115 VOCs measured were below 0.01 ppb.

[0130] 7) Determination of parallel samples: Analyze one parallel sample for every 10 samples or for every batch (less than 10 samples / batch). The relative deviation of the target analyte in the parallel samples should be ≤30%; otherwise, find the cause and re-analyze.

[0131] 8) Internal standard: The retention time of the internal standard in the sample should not deviate from the retention time of the internal standard in the continuous calibration on the same day or the most recently drawn standard curve by no more than 20s, and the change in the quantitative ion peak area should be between 60% and 140%.

[0132] (4) Construction and evaluation of VOCs source component spectra.

[0133] (4.1) Construction of VOCs source component spectra

[0134] A total of 17 samples were collected from five industries: automobile manufacturing (2 companies, 3 outlets, 3 samples), electric bicycle manufacturing (3 companies, 3 outlets, 3 samples), plastic products manufacturing (5 companies, 5 outlets, 5 samples), footwear manufacturing (1 company, 3 outlets, 3 samples), and packaging and printing (3 companies, 3 outlets, 3 samples).

[0135] Furthermore, the source component spectra for each industry were constructed using the geometric arithmetic mean method mentioned earlier, such as... Figure 8 and Figure 9 As shown.

[0136] (4.2) Evaluation of VOCs source composition profiles

[0137] The divergence coefficient method mentioned above is used to determine the differences and similarities of the source component spectra and to evaluate them.

[0138] The divergence coefficients of the different sub-source class source compositions of the solvent used in this embodiment, calculated using the divergence coefficient method described above, are shown in the table below:

[0139] industry Automobile manufacturing electric bicycle manufacturing Plastics manufacturing industry Footwear industry Packaging Printing Automobile manufacturing - 0.58 0.61 0.78 0.63 electric bicycle manufacturing - - 0.45 0.73 0.48 Plastics manufacturing industry - - - 0.75 0.44 Footwear industry - - - - 0.66 Packaging Printing - - - - -

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A rapid method for constructing and evaluating VOCs source component spectra, characterized in that: Includes the following steps: Step S1: Conduct on-site investigation to determine the target VOCs emission source sampling enterprises, sampling port locations, and sampling methods; Step S2: Collect target VOCs source samples on-site using air bags or Summa canisters; Step S3: The sample is sent to a vehicle-mounted VOCs online analysis laboratory located near the sampling source within 1 to 2 hours after collection, and analyzed and measured using analytical instruments; The vehicle-mounted VOCs online analysis laboratory includes a dilution system and an analysis system. The dilution system uses high-purity nitrogen to dilute the concentration of the source sample to the detection range of the analysis instrument. A handheld gas detector is used to measure the total VOCs concentration at the sampling port, and the specific dilution factor is calculated by combining the source emission VOCs concentration with the detection limit of the analysis instrument. The analysis system connects the diluted source sample to the analysis instrument via an inert tubing for analysis. The dilution system includes a dilution tank, an inlet, an outlet, and a high-purity nitrogen cylinder. The dilution tank is the main body of the system, simultaneously introducing source sample waste gas and high-purity nitrogen at a predetermined volume ratio into a clean gas bag containing no gas. The dilution tank has two inlets: a sample gas inlet and a high-purity nitrogen inlet. The sample gas inlet is connected to the source sampling gas bag, and the nitrogen inlet is connected to the high-purity nitrogen cylinder via a rubber tube. The dilution tank has one outlet, which connects to the sample gas bag after mixing and dilution at different volume ratios. After the sample gas and high-purity nitrogen are connected to the dilution system, the inlet ratio of high-concentration source sample gas to high-purity nitrogen is set in the software interface of the dilution system. Before each injection, the inlet and outlet pipelines are purged with high-purity nitrogen. The diluted and mixed sample gas enters a new clean gas bag through the outlet. When the sampling volume in the new gas bag reaches 75% to 85% of the maximum volume of the gas bag, the dilution process ends. The diluted sample gas bag is then connected to the inlet of the analyzer for the analysis and determination of the volume concentration of VOCs species. Step S4: Based on the measured VOCs sample data from multiple emission sources of the same type, construct and evaluate the source composition profile of VOCs of this type; Among them, the geometric arithmetic mean method was used to construct the source component spectrum, and the number of samples of the same source class was at least three; the divergence coefficient method was used to evaluate the differences and similarities of the source component spectra. The source component spectra were constructed using the geometric arithmetic mean method, including: (1) The volume concentration of VOC species was determined based on the analysis of the diluted sample, and converted into mass concentration using the following formula; In the formula: C Q The mass concentration of VOC species, in μg / m³ 3 C V ppbv represents volume concentration or volume mixing ratio; M represents molecular weight; V represents volume concentration or volume mixing ratio. m The value is the molar volume of the gas, in g / mol, which is 22.4 L / mol under standard conditions. (2) Calculate the proportion of the mass concentration of all measured VOC species to the total mass concentration, i.e., the mass percentage of all measured VOC species. The data for each source sample is the mass percentage of all measured VOC species in that sample. (3) Source sample data from the same source class are collected and analyzed, and source component spectra are constructed using the geometric arithmetic mean method. The mean and standard deviation are calculated. The formula for calculating the average content of VOC species in the source component spectra is as follows: ； In the formula: Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; Number of source samples; The formula for calculating the standard deviation of VOC species content in the source component spectrum is as follows: ； In the formula: Species in a certain type of source spectrum to be constructed Standard deviation of content, % Species in a certain type of source spectrum to be constructed Average content, % , , , ..., The content (%) of VOCs species m in different samples of a certain source class; This represents the number of source samples.

2. The method for constructing and evaluating VOCs source component spectra according to claim 1, characterized in that: In step S1, the steps for determining the target VOCs emission source, sampling port location, and sampling method through on-site investigation include: Collect and organize environmental statistics data, pollution source emission inventories, and pollution census data for the target area; select typical VOCs emission sources for on-site investigation to obtain basic information, pollution removal facilities, and pollutant emission information of key VOCs emission sources in the target area; and determine typical target sampling sources and their sampling port locations that can represent the target area based on the investigation results.

3. The method for constructing and evaluating VOCs source component spectra according to claim 1, characterized in that: The steps for on-site collection of target VOCs source samples using air bags include: Step S211: Before sampling, place the gas bag directly into the vacuum sampling box, connect the valve on the gas bag to the gas supply line in the sampling box, and close and seal the sampling vacuum box; Step S212: For industrial enterprises, coal-fired power plants, and catering sources, insert the heated sampler into the sampling port of the end exhaust chimney of the target source, so that the front end of the sampler nozzle is close to the center area of ​​the chimney pipe, or extend the front end of the heated sampler nozzle directly to the middle of the exhaust chimney opening of the target source; for motor vehicles, extend the front end of the heated sampler nozzle directly to the position near the vehicle exhaust outlet; if the exhaust gas temperature inside the chimney or the vehicle exhaust temperature is higher than the ambient temperature, activate the heating of the sampling tube to make it consistent with the exhaust gas temperature inside the chimney or the vehicle exhaust temperature; Step S213: Connect the end of the heated sampler to the air inlet of the vacuum sampling box using a polytetrafluoroethylene connecting tube; start the vacuum pump in the vacuum sampling box to maintain a negative pressure inside the sampling box, so that the gas bag begins to collect waste gas samples; when the sampling volume in the gas bag reaches 75%~85% of the maximum volume of the gas bag, turn off the vacuum pump and end the sampling. Step S214: Quickly open the vacuum sampling box, close the gas bag valve, remove the sampling gas bag, and place it in a light-proof container; then quickly transfer it to the vehicle-mounted VOCs online analysis laboratory for analysis and measurement.

4. The method for constructing and evaluating VOCs source component spectra according to claim 1, characterized in that: The steps for on-site collection of target VOCs source samples using a Summa canister include: Step S221: Before sampling, use a fully automated cleaning device to clean the SUMMA canisters; after cleaning, evacuate the SUMMA canisters and set them aside for use; for every 20 SUMMA canisters cleaned, at least one canister should be injected with high-purity nitrogen for analysis to determine whether the cleaning process is clean; after cleaning, the SUMMA canisters that have been used for source sample collection should be analyzed for background contaminants before the next use to ensure that they are clean. Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuum-evacuated SUMMA canister is brought to the sampling point; the end of the heated sampler is connected to the air inlet of the SUMMA canister, and a particulate matter and water vapor filter is installed at the front end of the air inlet; for industrial enterprises, coal-fired power plants, and catering sources, the front end of the heated sampler is inserted into the sampling port of the end exhaust chimney of the target enterprise, so that the front end of the sampler is close to the center area of ​​the chimney pipe, or the front end of the heated sampler is directly extended to the middle of the exhaust chimney opening of the target source; for motor vehicles, the front end of the heated sampler is directly extended to the position near the exhaust outlet of the motor vehicle; if the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is activated to make it consistent with the exhaust gas temperature inside the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the SUMMA canister is opened to start collecting exhaust gas samples, and after the pressure inside the canister is consistent with the sampling environment pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

5. The method for constructing and evaluating VOCs source component spectra according to claim 1, characterized in that: The divergence coefficient method was used to assess the differences and similarities in the component spectra of different VOCs sources. The formula for calculating the divergence coefficient CD is as follows: ； In the formula: To compare the first table Class source component spectrum and the first The divergence coefficient defined in the source component spectrum; To include the number of species in the calculation, the number of individuals is [number missing]. For the first In the class component spectrum, the first The quality fraction of each species, % If CD approaches 0, it indicates that the component spectra are more similar; when CD ≥ 0.4, it indicates that the differences between the source component spectra are relatively large; when 0.2 ≤ CD < 0.4, the source component spectra are similar; when CD < 0.2, the source component spectra are somewhat similar.

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