Rapid VOCs source component spectrum construction and evaluation method

Abstract

The invention relates to a rapid VOCs source component spectrum construction and evaluation method. The method comprises the following steps of S1, performing field investigation and survey to determine a target VOCs emission source, a sampling port position and a sampling mode; s2, carrying out on-site collection on a target VOCs source sample by utilizing an air bag or a Suma tank; s3, the sample is sent to a vehicle-mounted VOCs online analysis laboratory staying near a sampling source within 1-2 hours after being collected, and analysis and determination are conducted through an analysis instrument; and S4, based on the measured data of the plurality of VOCs samples of the same type of emission sources, constructing and evaluating the VOCs source component spectrum of the source type. According to the present invention, the on-site sampling and analysis determination method is adopted, the rationality of the on-site sampling method and the dilution scheme of the high concentration VOCs source sample are improved so as to achieve the detection range of the analysis instrument, and the timeliness and the accuracy of the obtained data are improved.

Description

Technical Field

[0001] The present invention relates to the field of air pollution prevention and control, and in particular to a method for rapidly constructing and evaluating a VOCs source component spectrum. Background Art

[0002] Volatile organic compounds (VOCs) are key precursors to ozone formation. Research indicates that most cities and regions with ozone pollution fall within VOC-controlled zones. Therefore, research on the characteristics and source analysis of environmental VOC pollution plays a crucial role in the effective prevention and control of atmospheric ozone pollution.

[0003] Receptor models are the mainstream technical approach for source attribution of VOCs in the environment. Commonly used receptor models include positive definite matrix factorization (PMF) and chemical mass balance (CMB) models. The PMF model requires relevant source profile information to assign clear physical meaning to factors during factor identification, while the CMB model requires local source profiles as input for calculation. Therefore, VOC source profiles play a crucial and irreplaceable role in source attribution.

[0004] The current mainstream method or process for constructing VOCs source component profiles is to first collect samples on-site using air bags or Suma tanks, then transport the samples to the laboratory for analysis and measurement of VOCs species, and finally construct their source component profiles using mathematical or statistical methods. Despite this, there are two key issues that have not been well resolved to date: first, the traditional "VOCs source sample collection-laboratory analysis and determination-source component profile construction" method has poor timeliness, often requiring at least two weeks or even more than a month; second, during the long period of time from on-site source sample collection to laboratory analysis, VOCs species undergo significant chemical reaction transformations, making it difficult for the constructed source component profile to accurately represent the actual emission characteristics of typical VOCs sources.

[0005] Therefore, quickly and effectively constructing a source component spectrum that can accurately characterize VOCs emission sources can better support the practical application of VOCs source analysis 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 component spectrum construction and evaluation method that can quickly and accurately characterize the emission characteristics of volatile organic compounds (VOCs) sources, reduce the impact of chemical reaction conversion or loss of VOCs species, and significantly improve the timeliness and accuracy of VOCs source component spectrum construction, thereby enhancing the accuracy of environmental VOCs source analysis results, in order to more effectively support the prevention and control of atmospheric ozone pollution.

[0007] To achieve the above objectives, the present invention provides a rapid VOCs source component spectrum construction and evaluation method, 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: On-site collection of target VOCs source samples using air bags or Suma cans;

[0010] Step S3: The sample is delivered 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 analytical instrument of 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 within the detection range of the analysis instrument, wherein 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 and the upper detection limit of the analysis instrument; the analysis system connects the diluted source sample to the VOCs analysis instrument using an inert pipeline for analysis;

[0012] Step S4: Based on the measured data of multiple VOCs samples from the same type of emission source, construct and evaluate the VOCs source component spectrum of the source type;

[0013] Among them, the geometric arithmetic mean method is used to construct the source component spectrum, and the number of samples collected from the same type of target source is at least 3 or more; the divergence coefficient method is used to evaluate the differences and similarities of the source component spectrum.

[0014] Preferably, in step S1, the steps of conducting 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 include:

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

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

[0017] Step S211: Before sampling, place the air bag directly in the vacuum sampling box, connect the valve on the air bag to the gas pipeline 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, extend the heated sampler (including the front-end smoke gun and the rear-end heated sampling tube) into the sampling hole of the exhaust gas emission chimney at the end of the target source, so that the front end of the sampler smoke gun is close to the central area of ​​the chimney pipe, or directly extend the front-end smoke gun of the heated sampler to the middle position of the exhaust gas emission chimney (i.e., the emission port) of the target source; for motor vehicles, directly extend the front-end smoke gun of the heated sampler to a position close to the exhaust emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, start heating the sampling tube to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle;

[0019] Step S213: Using a polytetrafluoroethylene connecting tube, 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 in the sampling box, so that the air bag begins to collect the exhaust gas sample; when the sample volume in the air bag reaches 75% to 85% of the maximum volume of the air bag, turn off the vacuum pump, and end the sampling;

[0020] Step S214: quickly open the vacuum sampling box, close the air bag valve, take out the sampling air 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 of collecting target VOCs source samples on-site using a Suma tank include:

[0022] Step S221: Before sampling, the Suma can is cleaned using a fully automatic can cleaning device. After cleaning, the Suma can is evacuated and set aside for use. For every 20 Suma cans cleaned, at least one can is injected with high-purity nitrogen for analysis to determine if the cleaning process is clean. After cleaning, a Suma can previously used for source sample collection is analyzed for background contaminants before its next use to ensure thorough cleaning.

[0023] Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuumed Suma can 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 Suma can (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 hole of the terminal exhaust gas emission chimney of the target enterprise, 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 is directly extended to the middle position of the exhaust gas emission chimney (i.e., the emission port) of the target source; for motor vehicles, the front end of the heated sampler is directly extended to a position near the exhaust gas emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is started to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the Suma can is opened to start collecting exhaust gas samples. After the pressure in the can is consistent with the sampling ambient pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

[0024] Preferably, the high-concentration source samples after collection are sent to the dilution system in the vehicle-mounted laboratory for dilution. The dilution multiple or ratio mainly comes from the conversion of 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 VOCs online analyzer.

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

[0026] Among them, the dilution box is the main body of the dilution system, which can simultaneously pass the source sample exhaust gas and high-purity nitrogen at a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed;

[0027] Two air inlets in the dilution box: including 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 bottle through a rubber tube;

[0028] One outlet of the dilution box: connect to the sample gas bags after mixed and diluted with different volume ratios.

[0029] Preferably, after connecting the sample gas and high-purity nitrogen to the dilution system, the intake ratio of the high-concentration source sample gas and the 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, and the purge time is set to 10s to eliminate the interference of residual samples in the pipeline; the diluted and mixed sample gas enters the new clean air bag through the outlet, and the dilution process ends when the sampling volume in the new air bag reaches 75%~85% of the maximum volume of the air bag; the diluted sample air bag is connected to the sampling port of the analyzer to analyze and determine the volume concentration of VOCs species (unit: ppbv).

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

[0031] First, the volume concentration (ppbv) of VOCs species was determined based on the analysis of the diluted sample and converted into mass concentration (μg / m 3 )data:

[0032]

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

[0034] Then, calculate the ratio of the mass concentration of all measured VOCs species to the total mass concentration (that is, the sum of the mass concentrations of all measured VOCs species), that is, the mass proportion (unit, %). The data of each source sample is the mass proportion (%) of all VOCs species measured for the sample.

[0035] Finally, the source sample data collected and analyzed from the same source type (source sample quantity of at least 3 or more) are used to construct a source composition spectrum (including mean value and standard deviation) using the geometric arithmetic mean method. The calculation formula for the average content of VOCs species in the source composition spectrum is as follows:

[0036]

[0037] Where: Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples.

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

[0039]

[0040] Where: Species in a certain source spectrum constructed Standard deviation of content, %; Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples.

[0041] Preferably, the divergence coefficient method (CD) is used to evaluate the differences in the component spectra of different VOCs sources. The calculation formula of the CD is:

[0042]

[0043] Where: For comparison, Table Class source component spectrum and The divergence coefficient of the source component spectrum definition; The number of species included in the calculation, For the Class component spectrum Mass fraction of species, %;

[0044] The closer CD is to 0, the more similar the source component spectra are; when CD ≥ 0.4, the differences between the source component spectra are large; when 0.2 ≤ CD < 0.4, the source component spectra are similar; when CD < 0.2, the source component spectra have certain similarity.

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

[0046] The present invention significantly improves the timeliness of VOC source component profile construction, reducing the time from source sample collection to profile creation to less than 12 hours. This significantly enhances the accuracy and representativeness of the VOC source profile, avoids the influence of chemical reactions and conversions of VOC species during source sample collection and analysis, and allows for more accurate VOC source profile construction. The present invention also eliminates the cumbersome process of source sample collection from site to transport for laboratory analysis, reducing transportation and analysis costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0048] Figure 1 A step-by-step diagram for the rapid construction and evaluation of VOCs source component profiles;

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

[0050] Figure 3 This is a diagram of the on-site collection steps for target VOCs source samples using a Suma tank;

[0051] Figure 4 A process framework diagram for the rapid construction and evaluation of VOCs source component profiles;

[0052] Figure 5 Flowchart of the sample dilution process;

[0053] Figure 6 This is an example of a field survey report for VOCs emission sources;

[0054] Figure 7 Schematic diagram of the continuous monitoring system for atmospheric volatile organic compounds in an embodiment of the present invention;

[0055] Figure 8 The VOCs source component spectrum of the solvent use-related source class constructed in the embodiments of the present invention;

[0056] Figure 9 The solvent used in the embodiment of the present invention uses a VOCs source component spectrum for the automobile manufacturing industry, the electric bicycle manufacturing industry, the plastic product manufacturing industry, the shoemaking industry, and the packaging and printing industry. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0058] The present invention provides a rapid VOCs source component spectrum construction and evaluation method, such as Figure 1 、 Figure 4 As shown, the following steps are included:

[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, the on-site investigation to determine the target VOCs emission sources, sampling port locations and sampling methods includes: collecting and sorting out basic information such as environmental data, pollution source emission inventories and pollution survey data of the target area, selecting typical VOCs emission sources for on-site investigation, and obtaining basic information on key VOCs emission sources, pollution control facilities, and pollutant emission information in the target area; Figure 6 A preferred VOCs industrial or coal-fired power plant emission source field survey table is shown. Based on the survey results, a typical target sampling source and its sampling port location that can represent the target area are determined.

[0061] Step S2: Use air bags or Suma cans to collect target VOCs source samples on site.

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

[0063] Step S211: Before sampling, place the air bag in a vacuum sampling box, connect the valve on the air bag to the gas pipeline 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, extend the heated sampler (including the front-end smoke gun and the rear-end heated sampling tube) into the sampling hole of the terminal exhaust gas emission chimney of the target enterprise, so that the front end of the sampler smoke gun is close to the central area of ​​the chimney pipe, or the front-end smoke gun of the heated sampler is directly extended to the middle position of the exhaust gas emission chimney (i.e., the emission port) of the target source; for motor vehicles, extend the front-end smoke gun of the heated sampler directly to a position near the exhaust gas emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, start the heating of the sampling tube to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle.

[0065] Step S213: Use a polytetrafluoroethylene 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 in the sampling box, so that the air bag begins to collect exhaust gas samples; when the sampling volume in the air bag reaches 75%~85% of the maximum volume of the air bag, turn off the vacuum pump to end sampling.

[0066] Step S214: quickly open the vacuum sampling box, close the air bag valve, take out the sampling air 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 Suma tank include:

[0068] Step S221: Before sampling, the Suma can is cleaned using a fully automatic can cleaning device. After cleaning, the Suma can is evacuated and set aside for use. For every 20 Suma cans cleaned, at least one can is injected with high-purity nitrogen for analysis to determine if the cleaning process is clean. After cleaning, the Suma can previously used for source sample collection is analyzed for background contaminants before its next use to ensure that it is clean.

[0069] Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuumed Suma can 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 Suma can (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 hole of the terminal exhaust gas emission chimney of the target enterprise, 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 is directly extended to the middle position of the exhaust gas emission chimney (i.e., the emission port) of the target source; for motor vehicles, the front end of the heated sampler is directly extended to a position near the exhaust gas emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is started to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the Suma can is opened to start collecting exhaust gas samples. After the pressure in the can is consistent with the sampling ambient pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

[0070] It should be noted that quality control should be carried out during the sampling process: a cleaned and qualified Suma can should be used for sample collection; the front end of the sampler smoke gun should be positioned close to the center area of ​​the chimney pipe or the middle position of the exhaust gas outlet of the target source, and the length of the sampling tube should be 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] Among them, the analytical instrument of 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 within the detection range of the analytical instrument, wherein a handheld gas detector is used to measure the total VOCs concentration at the sampling port, and the specific dilution multiple is calculated based on the source emission VOCs concentration and the detection upper limit of the vehicle-mounted VOCs analyzer; the diluted and mixed sample gas enters a new clean air bag through the air outlet, and the dilution process ends when the sampling volume in the new air bag reaches 75%~85% of the maximum volume of the air bag; the diluted sample air bag is connected to the sampling port of the analytical instrument.

[0073] Each sample is placed in a light-proof container after collection and sent to the vehicle-mounted VOCs online analysis laboratory for timely analysis within 1-2 hours after collection to avoid chemical reaction consumption of active VOCs species. The vehicle-mounted 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 through a dilution system. The dilution multiple or ratio mainly comes from the conversion of 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 VOCs online analyzer.

[0075] Further, if Figure 5 As shown, the dilution system includes: a dilution box, an air inlet, an air outlet and a high-purity nitrogen bottle;

[0076] Among them, the dilution box is the main body of the dilution system, which can simultaneously pass the source sample exhaust gas and high-purity nitrogen at a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed;

[0077] Two air inlets in the dilution box: including 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 the high-purity nitrogen bottle through a rubber tube;

[0078] One outlet of the dilution box: connect to the sample gas bags after mixed and diluted with different volume ratios.

[0079] Preferably, after connecting the sample gas and high-purity nitrogen to the dilution system, the intake ratio of the high-concentration source sample gas and the 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, and the purge time is set to 10s to eliminate the interference of residual samples in the pipeline; the diluted and mixed sample gas enters the new clean air bag through the outlet, and the dilution process ends when the sampling volume in the new air bag reaches 75%~85% of the maximum volume of the air bag; the diluted sample air bag is connected to the sampling port of the analyzer to analyze and determine the volume concentration of VOCs species (unit: ppbv).

[0080] Sample analysis and determination: The diluted sample gas bag is connected to the analytical instrument with an inert pipeline for analysis. The analytical instrument can be a common VOCs online 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 of multiple emission sources of the same type, construct and evaluate the VOCs source component spectrum of the source type.

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

[0083] First, the volume concentration (ppbv) of VOCs species was determined based on the analysis of the diluted sample and converted into mass concentration (μg / m 3 )data:

[0084]

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

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

[0087] Finally, the source sample data collected and analyzed for the same source class (source sample quantity of at least 3 or more) are used to construct the source composition spectrum (including the mean value and standard deviation) of the source class using the geometric arithmetic mean method. The calculation formula for the average content of VOCs species in the source composition spectrum is as follows:

[0088]

[0089] Where: Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples.

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

[0091]

[0092] Where: Species in a certain source spectrum constructed Standard deviation of content, %; Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples.

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

[0094]

[0095] Where: For comparison, Table Class source component spectrum and The divergence coefficient of the source component spectrum definition; The number of species included in the calculation, For the Class component spectrum Mass fraction of species, %;

[0096] The closer CD is to 0, the more similar the component spectra are; when CD ≥ 0.4, the differences between the source component spectra are 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] The present invention adopts an on-site sampling and analysis and determination method. By improving the rationality of the on-site sampling method and the dilution scheme of high-concentration source VOCs samples, it brings them within the detection range of the analytical instrument, thereby improving the timeliness and accuracy of the obtained data.

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

[0099] (1) Conduct on-site investigation to determine the VOCs emission enterprises related to solvent use, sampling port locations and sampling methods.

[0100] We collected basic information such as Zhumadian's environmental statistics, pollution source emission lists, and pollution source census data, and conducted on-site investigations on solvent-related VOCs emission enterprises to determine the basic information, pollution control facilities, and pollutant emission status of key emission enterprises in Zhumadian. Figure 6 As shown in the on-site survey table of VOCs emission sources.

[0101] Based on on-site survey results, this example selected companies emitting VOCs from solvent-related sources. Under normal production conditions, air bags were used to collect samples from the chimney outlets of their production workshops. The selection of sampling locations, frequency, and timing for each company, as well as related procedures, were carried out in accordance with relevant industry standards.

[0102] (2) Use air bags to collect VOCs source samples related to solvent use on-site.

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

[0104] Air bag sampling process:

[0105] ① Before sampling, place the air bag directly in the vacuum sampling box, connect the valve on the air bag to the gas pipeline 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 port) of the solvent-using enterprise; if the exhaust gas temperature of the chimney is higher than the ambient temperature, start heating the sampling tube to keep it consistent with the exhaust gas temperature of the chimney;

[0107] ③Use a polytetrafluoroethylene 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 in the sampling box, so that the air bag begins to collect exhaust gas samples; when the sample volume in the air bag reaches 75% to 85% of the maximum volume of the air bag, turn off the vacuum pump and end sampling;

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

[0109] ⑤Measure and record the exhaust gas temperature, exhaust gas flow rate and moisture content in the exhaust duct, and the operating procedures shall comply with the provisions of relevant industry standards.

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

[0111] Quality control methods during air bag sampling: use new air bags when collecting samples; the front end of the sampler smoke gun is close to the middle of the chimney exhaust port, and the length of the sampling tube should be as short as possible.

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

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

[0114] (3.1) Sample dilution

[0115] The high-concentration source samples after collection are diluted through a dilution system. The dilution multiple or ratio mainly comes from the conversion of the total concentration of VOCs emitted from the source 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 VOCs online analyzer.

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

[0117] Among them, the dilution box is the main body of the dilution system, which can simultaneously pass the source sample exhaust gas and high-purity nitrogen at a certain volume ratio into a clean gas bag that does not contain any gas, so that they are fully and evenly mixed;

[0118] Two air inlets in the dilution box: including 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 the high-purity nitrogen bottle through a rubber tube;

[0119] One outlet of the dilution box: connect to the sample gas bags after mixed and diluted with different volume ratios.

[0120] After connecting the sample gas and high-purity nitrogen to the dilution system, set the intake ratio of high-concentration source sample gas and high-purity nitrogen (i.e., the dilution ratio) 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. The purge time is set to 10 seconds to eliminate the interference of residual samples in the pipeline; the diluted and mixed sample gas enters the new clean air bag through the outlet. When the sampling volume in the new air bag reaches 75%~85% of the maximum volume of the air bag, the dilution process ends.

[0121] (3.2) Sample analysis

[0122] The diluted sample bag is connected to the analytical instrument with an inert tube for analysis. The sample analysis is completed by the ZF-PKU-VOC1007 atmospheric volatile organic compound continuous monitoring instrument (GC-MS / FID). Figure 7 As shown in the figure, it is a working diagram of the ZF-PKU-VOC1007 atmospheric volatile organic compound continuous monitoring system. The sample is enriched by ultra-low temperature in an air pipe, and the VOCs species components are qualitatively and quantitatively analyzed using a gas chromatography-mass spectrometer.

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

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

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

[0126] 3) Detection limit test: The detection limits of 115 VOCs are all ≤ 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 115 VOCs in the measurement results were all below 0.01 ppb;

[0130] 7) Parallel sample analysis: Analyze one replicate for every 10 samples or each batch (if less than 10 samples / batch). The relative deviation of the target substance in the replicate samples should be ≤30%. If not, find the cause and reanalyze;

[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 20 seconds, and the change in the quantification ion peak area should be between 60% and 140%.

[0132] (4) Construction and evaluation of VOCs source composition spectrum.

[0133] (4.1) Construction of VOCs source composition spectrum

[0134] A total of 17 samples were collected from five industries, including automobile manufacturing (2 enterprises, 3 groups, 3 samples in total), electric bicycle manufacturing (3 enterprises, 3 groups, 3 samples in total), plastic products manufacturing (5 enterprises, 5 groups, 5 samples in total), shoemaking (1 enterprise, 3 groups, 3 samples in total), and packaging and printing (3 enterprises, 3 groups, 3 samples in total).

[0135] Furthermore, the geometric arithmetic mean method mentioned above was used to construct the source component spectrum of each industry, such as Figure 8 and Figure 9 shown.

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

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

[0138] According to the divergence coefficient method mentioned above, the divergence coefficients of the source component spectra of different sub-source types of the solvent source in this embodiment are calculated and shown in the following table:

[0139] industry automotive manufacturing Electric bicycle manufacturing industry Plastic products manufacturing industry shoemaking industry packaging printing automotive manufacturing - 0.58 0.61 0.78 0.63 Electric bicycle manufacturing industry - - 0.45 0.73 0.48 Plastic products manufacturing industry - - - 0.75 0.44 shoemaking industry - - - - 0.66 packaging printing - - - - -

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention. They should all be included in the scope of the technical solution for protection of the present invention.

Claims

1. A rapid VOCs source component profile construction and evaluation method, characterized by: The steps include: Step S1: Conduct on-site investigation to determine the target VOCs emission source sampling enterprise, sampling port location and sampling method; Step S2: On-site collection of target VOCs source samples using air bags or Suma cans; Step S3: The sample is delivered 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 analytical instrument of 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 within the detection range of the analysis instrument, wherein 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 and the upper detection limit of the analysis instrument; the analysis system connects the diluted source sample to the analysis instrument with an inert pipeline for analysis; Step S4: Based on the measured data of multiple VOCs samples of the same type of emission source, construct and evaluate the VOCs source component spectrum of the source type; Among them, the geometric arithmetic mean method is used to construct the source component spectrum, and the number of samples of the same source type is at least 3 or more; the divergence coefficient method is used to evaluate the differences and similarities of the source component spectrum.

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

3. The VOCs source component spectrum construction and evaluation method 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 air bag directly in the vacuum sampling box, connect the valve on the air bag to the gas pipeline in the sampling box, and close and seal the sampling vacuum box; Step S212: For industrial enterprises, coal-fired power plants and catering sources, the heated sampler is inserted into the sampling hole of the exhaust gas emission chimney at the end of the target source, so that the front end of the sampler smoke gun is close to the central area of ​​the chimney pipe, or the front end smoke gun of the heated sampler is directly extended to the middle position of the exhaust gas emission chimney of the target source; for motor vehicles, the front end smoke gun of the heated sampler is directly extended to a position close to the exhaust emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube is started to heat up to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle; Step S213: Using a polytetrafluoroethylene connecting tube, 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 in the sampling box, so that the air bag begins to collect the exhaust gas sample; when the sample volume in the air bag reaches 75% to 85% of the maximum volume of the air bag, turn off the vacuum pump, and end the sampling; Step S214: quickly open the vacuum sampling box, close the air bag valve, take out the sampling air 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 VOCs source component spectrum construction and evaluation method according to claim 1, characterized in that: The steps for on-site collection of target VOCs source samples using a Suma tank include: Step S221: Before sampling, the Suma can is cleaned using a fully automatic can cleaning device. After cleaning, the Suma can is evacuated and set aside for use. For every 20 Suma cans cleaned, at least one can is injected with high-purity nitrogen for analysis to determine if the cleaning process is clean. After cleaning, the Suma can previously used for source sample collection is analyzed for background contaminants before its next use to ensure that it is clean. Step S222: Sampling is performed using an instantaneous sampling method; the cleaned and vacuumed Suma can is brought to the sampling point; the end of the heated sampler is connected to the air inlet of the Suma can, 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 hole of the terminal exhaust gas emission chimney of the target enterprise, 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 is directly extended to the middle position of the exhaust gas emission chimney of the target source; for motor vehicles, the front end of the heated sampler is directly extended to a position near the exhaust gas emission port of the motor vehicle; if the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle is higher than the ambient temperature, the sampling tube heating is started to keep it consistent with the exhaust gas temperature in the chimney or the exhaust gas temperature of the motor vehicle; the air inlet valve of the Suma can is opened to start collecting exhaust gas samples. After the pressure in the can is consistent with the sampling ambient pressure, the valve is closed and sealed with a sealing cap, and the sampling is completed.

5. The VOCs source component spectrum construction and evaluation method according to claim 1, characterized in that: The dilution system includes: a dilution box, an air inlet, an air outlet and a high-purity nitrogen bottle; Among them, the dilution box is the main body of the dilution system, which simultaneously introduces the source sample exhaust gas and high-purity nitrogen with a determined volume ratio into a clean gas bag that does not contain any gas; Two air inlets in the dilution box: including 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 bottle through a rubber tube; One outlet of the dilution box: connect to the sample gas bags after mixed and diluted with different volume ratios.

6. The VOCs source component spectrum construction and evaluation method according to claim 5, characterized in that: After connecting the sample gas and high-purity nitrogen to the dilution system, set the intake ratio of the high-concentration source sample gas and high-purity nitrogen in the software operation interface of the dilution system. Purge the inlet and outlet pipes with high-purity nitrogen before each injection. 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%~85% of the maximum volume of the gas bag, the dilution process ends. Connect the diluted sample gas bag to the sampling port of the analyzer to analyze and determine the volume concentration of VOCs species.

7. The VOCs source component spectrum construction and evaluation method according to claim 1, characterized in that: The geometric arithmetic mean method is used to construct the source component spectrum, including: (1) Determine the volume concentration of VOCs species based on the analysis of the diluted sample and convert it into mass concentration using the following formula; Where: C Q Represents the mass concentration of VOC species, μg / m 3 ; C V represents volume concentration or volume mixing ratio, ppbv; M represents molecular mass; V m is the gas molar volume, g / mol, which is 22.4 L / mol under standard conditions; (2) Calculate the ratio of the mass concentration of all measured VOCs species to the total mass concentration, that is, the sum of the mass concentrations of all measured VOCs species, that is, the mass proportion. The data of each source sample is the mass proportion of all VOCs species measured for that sample; (3) The source sample data collected and analyzed from the same source type are used to construct a source component spectrum using the geometric arithmetic mean method, and the mean value and standard deviation are calculated. The calculation formula for the average content of VOCs species in the source component spectrum is as follows: Where: Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples; The calculation formula for the standard deviation of the VOCs species content in the source component spectrum is as follows: Where: Species in a certain source spectrum constructed Standard deviation of content, %; Species in a certain source spectrum constructed The average content of ,%; , , ,……, is the content of VOCs species m in different samples of a certain source type, %; is the number of source samples.

8. The VOCs source component spectrum construction and evaluation method according to claim 1, characterized in that: The divergence coefficient method is used to evaluate the differences and similarities of the component spectra of different VOCs sources. The calculation formula of the divergence coefficient CD is: Where: For comparison, Table Class source component spectrum and The divergence coefficient of the source component spectrum definition; The number of species included in the calculation, For the Class component spectrum Mass fraction of species, %; The closer CD is to 0, the more similar the component spectra are; when CD ≥ 0.4, the differences between the source component spectra are large; when 0.2 ≤ CD < 0.4, the source component spectra are similar; when CD < 0.2, the source component spectra are somewhat similar.

Images