Online analysis method and equipment for VOCs components in atmospheric particulate matter

Abstract

The present invention provides an online analysis method and device for VOCs components in atmospheric particulate matter. The present invention can detect VOCs components in particulate matter online, and its real-time performance is good and the detection speed is fast. At the same time, the present invention uses light heating and electric heating to dissociate particulate matter, and uses proton transfer mass spectrometry (PTR) for detection, which reduces the influence of fragmentation peaks and ensures the accuracy of the measurement results.

Description

Technical Field

[0001] The present invention relates to the technical field of VOCs analysis, and in particular to an online analysis method and equipment for VOCs components in atmospheric particulate matter. Background Art

[0002] In order to monitor the air quality, it is often necessary to analyze the VOCs contained in atmospheric particulate matter. VOCs (volatile organic compounds) refer to volatile organic compounds, which refer to organic compounds with a saturated vapor pressure greater than 133.32 Pa at room temperature and a boiling point below 50-260°C at normal pressure, or any organic solid or liquid that can volatilize at room temperature and pressure, which are very harmful to the human body. In order to analyze the specific components of VOCs, the current method is mainly to collect atmospheric gas samples at the measurement point and then bring them back to the laboratory for analysis. Its real-time performance is poor and the operation is complicated, which is not conducive to the rapid analysis of VOCs components contained in atmospheric particulate matter. Therefore, it is necessary to propose further solutions to the above problems. Summary of the invention

[0003] The present invention aims to provide an online analysis method and device for VOCs components in atmospheric particulate matter to overcome the deficiencies in the prior art.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] An online analysis method for VOCs components in atmospheric particulate matter, comprising:

[0006] During the time period t1, the particles of preset particle size in the air are filtered, and the filtered air is passed into the PTR mass spectrometer to measure the basic components in the air and the mass m1 of the filtered particles is measured at the same time;

[0007] During the t2 period, filtered air is continuously introduced and heated to dissociate fine particles that can pass through the filter membrane. The PTR mass spectrometer measures the basic components in the air and the VOCs components volatilized by the heated fine particles, and at the same time measures the mass m2 of the filtered particles;

[0008] During the time period t3, the air supply is stopped, and dry gas is blown toward the filtered particulate matter, and the mass m3 of the filtered particulate matter after drying is measured;

[0009] During the t4 period, the filtered particulate matter is photo-heated to volatilize the VOCs in the particulate matter. After further electrical heating and dissociation, the cold trap is concentrated and the VOCs components in the atmospheric particulate matter are measured by PTR mass spectrometry. At the same time, the mass m4 of the remaining particulate matter after photo-heating and dissociation is measured.

[0010] Among them, (m3-m4) / m3 is the proportion of VOCs in particulate matter, and the results of PTR mass spectrometry are used to evaluate the composition of VOCs in atmospheric particulate matter.

[0011] In order to solve the above technical problems, the technical solution of the present invention is:

[0012] An online analysis device for VOCs components in atmospheric particulate matter, comprising: a gas cylinder, a particulate matter gas source, a weighing module, an optical heating module, an electric heating module, a refrigeration module, an air pump and a PTR mass spectrometer;

[0013] The gas cylinder and the particulate gas source are respectively connected to the inlet end of the weighing module through pipes. The weighing module includes: a filter membrane, a lower cavity, and a conical tube. The filter membrane is located at the inlet of the lower cavity, and the conical tube is located at the outlet of the lower cavity. The optical heating module is arranged toward the filter membrane. The outlet end of the weighing module is connected to the PTR mass spectrometer through a pipe. The electric heating module and the refrigeration module are arranged between the outlet end of the weighing module and the PTR mass spectrometer. The vacuum pump is connected between the outlet end of the weighing module and the electric heating module through a pipe.

[0014] Preferably, a first solenoid valve is provided on the pipeline connecting the gas cylinder to the inlet end of the weighing module, a second solenoid valve is provided on the pipeline connecting the particulate gas source to the inlet end of the weighing module, and a third solenoid valve is provided on the pipeline connecting the vacuum pump to the outlet end of the weighing module and the electric heating module.

[0015] Preferably, the particulate matter gas source is the atmosphere or a smoke chamber capable of generating particles.

[0016] Preferably, a cutting head for selecting a particle size range is provided on the pipeline connecting the particulate gas source to the inlet end of the weighing module.

[0017] Preferably, the optical heating module comprises: a cover body buckled on the weighing module and an LED lamp arranged on the inner side surface of the cover body and facing the filter membrane.

[0018] Preferably, the inner side surface is an inclined surface, and there are multiple LED lamps, which are circumferentially distributed on the inclined surface at equal intervals.

[0019] Preferably, the online analysis equipment also includes: a first buffer chamber and a second buffer chamber, the gas cylinder, the particulate gas source, and the inlet end of the weighing module are commonly connected to the first buffer chamber, and the outlet end of the weighing module, the vacuum pump, and the PTR mass spectrometer are commonly connected to the second buffer chamber.

[0020] Preferably, the electric heating module comprises a heating wire, and the refrigeration module comprises: a multi-layer semiconductor refrigeration sheet, a heat conductor and a capillary stainless steel tube arranged on the multi-layer semiconductor refrigeration sheet, and a ceramic heating block arranged on the heat conductor.

[0021] Preferably, the online analysis device further comprises a water tank connected to the PTR mass spectrometer.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the present invention can detect VOCs components in particulate matter online, has good real-time performance, and has a fast detection speed. At the same time, the present invention uses light heating and electric heating to dissociate particulate matter, and uses proton transfer mass spectrometry (PTR) for detection, which reduces the influence of fragmentation peaks and ensures the accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic plan view of the online analysis device for VOCs components in atmospheric particulate matter of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides an online analysis method for VOCs components in atmospheric particulate matter, which comprises the following steps:

[0027] During the time period t1, the particles of preset particle size in the air are filtered, and the filtered air is passed into the PTR mass spectrometer to measure the basic components in the air and the mass m1 of the filtered particles is measured at the same time;

[0028] During the t2 period, filtered air is continuously introduced and heated to dissociate fine particles that can pass through the filter membrane. The PTR mass spectrometer measures the basic components in the air and the VOCs components volatilized by the heated fine particles, and at the same time measures the mass m2 of the filtered particles;

[0029] During the time period t3, the air supply is stopped, and dry gas is blown toward the filtered particulate matter, and the mass m3 of the filtered particulate matter after drying is measured;

[0030] During the t4 period, the filtered particulate matter is photo-heated to volatilize the VOCs in the particulate matter. After further electrical heating and dissociation, the cold trap is concentrated and the VOCs components in the atmospheric particulate matter are measured by PTR mass spectrometry. At the same time, the mass m4 of the remaining particulate matter after photo-heating and dissociation is measured.

[0031] Among them, (m3-m4) / m3 is the proportion of VOCs in particulate matter, and the results of PTR mass spectrometry are used to evaluate the composition of VOCs in atmospheric particulate matter.

[0032] Thus, by calculating the difference between m4 and m3, the mass of VOCs in the particulate matter can be obtained; by PTR, the composition of VOCs can be obtained; by calculating the mass difference between m3 and m2, the moisture content in the particulate matter can be obtained. When conducting an assessment, the air quality represented can be evaluated based on the composition of VOCs measured by the PTR mass spectrometer.

[0033] In addition, it should be noted that t1, t2, t3, and t4 are continuous time periods, that is, t2 starts when t1 ends and ends when t3 starts. When uninterrupted measurement is required, two identical parts can be made to work simultaneously, and at this time, t3+t4<t1+t2 is satisfied, where the time length of t1 can be equal to the time length of t2.

[0034] like Figure 1 As shown, the present invention also provides an online analysis device for VOCs components in atmospheric particulate matter, which includes: a gas cylinder 1, a particulate gas source, a weighing module, an optical heating module, an electric heating module 13, a refrigeration module 14, an exhaust pump 17 and a PTR mass spectrometer 19.

[0035] The gas source is used to provide dry gas, which is connected to the inlet end of the weighing module through a pipeline. The dry gas is preferably helium, which has stable chemical properties and will not participate in the reaction and affect the detection results. Accordingly, a first solenoid valve 2 is provided on the pipeline connecting the gas cylinder 1 to the inlet end of the weighing module.

[0036] The particulate matter gas source is used to provide a gas sample containing particulate matter to be detected. According to the source of the gas sample, the particulate matter gas source can be the atmosphere or a smoke chamber 4 that can provide particulate matter through reaction. The particulate matter gas source is connected to the inlet end of the weighing module through a pipeline. Accordingly, a second solenoid valve 5 is provided on the pipeline connecting the particulate matter gas source to the inlet end of the weighing module.

[0037] The weighing module is used to achieve filtering and weighing. Specifically, the main structure of the weighing module is: a filter membrane 9, a lower cavity 10, and a conical tube 11.

[0038] The filter membrane 9 is located at the inlet of the lower cavity 10, and the filter membrane 9 is a quartz filter membrane 9. At this time, particles with a particle size of 100nm can pass through the filter membrane 9, thereby ensuring that particles of 2.5um-100nm are retained on the filter membrane 9. The conical tube 11 is located at the outlet of the lower cavity 10.

[0039] The measuring principle of the weighing module is based on the micro-oscillation balance method. Specifically, the micro-oscillation balance method uses an oscillating hollow conical tube 11 in the mass sensor, and a replaceable filter membrane 9 is installed at its oscillation end. The oscillation frequency depends on the characteristics of the conical tube 11 and its mass. When the sampled airflow passes through the filter membrane 9, the particles therein are deposited on the filter membrane 9. The change in the mass of the filter membrane 9 causes the change in the oscillation frequency. The mass of the particles deposited on the filter membrane 9 is calculated by the change in the oscillation frequency. Since it belongs to an existing measurement method, the present invention does not introduce it in detail.

[0040] A cutting head 3 for selecting a particle size range is arranged on the pipeline connecting the particle gas source to the inlet end of the weighing module. The cutting head 3 selects the particle size by its own pumping speed. The cutting head 3 is an existing product, for example, a cutting head 3 with a model of URG-2000-30ED can be used.

[0041] The optical heating module is arranged toward the filter membrane 9, and is used to optically heat the particles trapped on the filter membrane 9. In this way, the VOCs in the particles are volatilized and enter the PTR mass spectrometer 19 for detection. At the same time, the components of the VOCs are not destroyed, thus ensuring the accuracy of the measurement results.

[0042] In one embodiment, the optical heating module comprises: a cover body 7 buckled on the weighing module and an LED lamp 8 arranged on the inner side of the cover body 7 and facing the filter membrane 9. In order to ensure uniform heating, the inner side is an inclined surface, and there are multiple LED lamps 8, which are evenly spaced and circumferentially distributed on the inclined surface. Preferably, the angle of the inclined surface is 45°, and the number of LED lamps 8 is 8.

[0043] The outlet end of the weighing module is connected to the PTR mass spectrometer 19 through a pipeline, and the electric heating module 13 and the refrigeration module 14 are arranged between the outlet end of the weighing module and the PTR mass spectrometer 19 .

[0044] Among them, the electric heating module 13 is used to heat the particulate matter passing through the filter membrane 9 so that the VOCs are volatilized and enter the PTR mass spectrometer 19 for component detection. The electric heating module 13 includes a heating wire. The refrigeration module 14 is used to first condense the organic matter by refrigeration, and then volatilize it by heating so that it can enter the mass spectrometer in the next step. Specifically, the refrigeration module 14 is a cold trap structure, which includes: a multi-layer semiconductor refrigeration sheet, a heat conductor and a capillary stainless steel tube arranged on the multi-layer semiconductor refrigeration sheet, and a ceramic heating block arranged on the heat conductor. Thereby, the organic matter can be condensed onto the wall of the stainless steel capillary tube.

[0045] The vacuum pump 17 is used to pump the gas sample into the PTR mass spectrometer 19, and is connected to the outlet of the weighing module and the electric heating module 13 through a pipeline. Correspondingly, a third solenoid valve 16 is provided on the pipeline between the outlet of the weighing module and the electric heating module 13 connected to the vacuum pump 17.

[0046] In order to ensure the stability of the airflow, the online analysis device further includes: a first buffer chamber 6 and a second buffer chamber 12. At this time, the gas cylinder 1, the particulate gas source, and the inlet end of the weighing module are connected to the first buffer chamber 6, and the outlet end of the weighing module, the air pump 17, and the PTR mass spectrometer 19 are connected to the second buffer chamber 12.

[0047] The online analysis device further includes a water tank 18 connected to the PTR mass spectrometer 19 , and a mass flow meter 15 located on an inlet pipe of the PTR mass spectrometer 19 .

[0048] When the online analysis device for VOCs components in atmospheric particulate matter of the present invention is working:

[0049] First, the first solenoid valve 2 is closed, the second solenoid valve 5 is opened, the third solenoid valve 16 is opened, the vacuum pump 17 is turned on, the optical heating module is turned off, the electric heating block is turned off, the refrigeration module 14 is turned on for concentration, and the weighing module measures the particle concentration online. After t1 time, VOC volatilizes into the PTR mass spectrometer 19. The PTR mass spectrometer 19 obtains gas data under normal conditions, and the weighing module obtains the particle mass m1.

[0050] Then, the first solenoid valve 2 is closed, the second solenoid valve 5 is opened, the third solenoid valve 16 is opened, the vacuum pump 17 is turned on, the optical heating module is closed, the electric heating block is turned on, the refrigeration module 14 is turned on for concentration, and the weighing module measures the particle concentration online. After t2 time, VOC volatilizes into the PTR mass spectrometer 19. The PTR mass spectrometer 19 obtains the fine particles + VOCs data under normal conditions, and the weighing module obtains the particle mass m2.

[0051] Then, the first solenoid valve 2 is opened, the second solenoid valve 5 is closed, the third solenoid valve 16 is closed, the vacuum pump 17 is closed, the optical heating module is closed, the electric heating block is closed, the refrigeration module 14 is opened for concentration, and the weighing module measures the particle concentration online. After t3 time, VOC volatilizes into the PTR mass spectrometer 19. The PTR mass spectrometer 19 obtains the fine particles + VOCs data under normal conditions, and the weighing module obtains the mass of the dried particles m3.

[0052] Finally, the first solenoid valve 2 is opened, the second solenoid valve 5 is closed, the third solenoid valve 16 is closed, the vacuum pump 17 is closed, the optical heating module is turned on, the electric heating block is turned on, the refrigeration module 14 is turned on for concentration, and the weighing module measures the particle concentration online. After t4 time, VOCs volatilize into the PTR mass spectrometer 19. The PTR mass spectrometer 19 obtains the VOCs data in the particles, and the weighing module obtains the mass of the particles after the VOCs volatilize m4.

[0053] In summary, the present invention can detect VOCs components in particulate matter online, and its real-time performance is good and the detection speed is fast. At the same time, the present invention uses light heating and electric heating to dissociate particulate matter, and uses proton transfer mass spectrometry (PTR) for detection, which reduces the influence of fragmentation peaks and ensures the accuracy of the measurement results.

[0054] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0055] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An online analysis method for VOCs components in atmospheric particulate matter, characterized in that: The online analysis method comprises: During the time period t1, the particles of preset particle size in the air are filtered, and the filtered air is passed into the PTR mass spectrometer to measure the basic components in the air and the mass m1 of the filtered particles is measured at the same time; During the t2 period, filtered air is continuously introduced and heated to dissociate fine particles that can pass through the filter membrane. The PTR mass spectrometer measures the basic components in the air and the VOCs components volatilized by the heated fine particles, and at the same time measures the mass m2 of the filtered particles; During the time period t3, the air supply is stopped, and dry gas is blown toward the filtered particulate matter, and the mass m3 of the filtered particulate matter after drying is measured; During the t4 period, the filtered particulate matter is photo-heated to volatilize the VOCs in the particulate matter. After further electrical heating and dissociation, the cold trap is concentrated and the VOCs components in the atmospheric particulate matter are measured by PTR mass spectrometry. At the same time, the mass m4 of the remaining particulate matter after photo-heating and dissociation is measured. Among them, (m3-m4) / m3 is the proportion of VOCs in particulate matter, and the results of PTR mass spectrometry are used to evaluate the composition of VOCs in atmospheric particulate matter.

2. An online analysis device for VOCs components in atmospheric particulate matter, characterized in that: The online analysis equipment includes: a gas cylinder, a particulate gas source, a weighing module, an optical heating module, an electric heating module, a refrigeration module, an air pump and a PTR mass spectrometer; The gas cylinder and the particulate gas source are respectively connected to the inlet end of the weighing module through pipelines. The weighing module includes: a filter membrane, a lower cavity, and a conical tube. The filter membrane is located at the inlet of the lower cavity, and the conical tube is located at the outlet of the lower cavity. The optical heating module is arranged toward the filter membrane. The outlet end of the weighing module is connected to the PTR mass spectrometer through a pipeline. The electric heating module and the refrigeration module are arranged between the outlet end of the weighing module and the PTR mass spectrometer. The vacuum pump is connected between the outlet end of the weighing module and the electric heating module through a pipeline. The particulate matter gas source is the atmosphere or a smoke chamber capable of generating particles; a cutting head for selecting a particle size range is arranged on a pipeline connected to the inlet end of the particulate matter gas source and the weighing module.

3. The online analysis device for VOCs components in atmospheric particulate matter according to claim 2 is characterized in that: A first solenoid valve is arranged on the pipeline connecting the gas cylinder to the inlet end of the weighing module, a second solenoid valve is arranged on the pipeline connecting the particulate gas source to the inlet end of the weighing module, and a third solenoid valve is arranged on the pipeline connecting the vacuum pump to the outlet end of the weighing module and the electric heating module.

4. The online analysis device for VOCs components in atmospheric particulate matter according to claim 2 is characterized in that: The optical heating module comprises: a cover body buckled on the weighing module and an LED lamp arranged on the inner side of the cover body and facing the filter membrane.

5. The online analysis device for VOCs components in atmospheric particulate matter according to claim 4 is characterized in that: The inner side surface is an inclined surface, and there are a plurality of LED lamps, which are circumferentially distributed on the inclined surface at equal intervals.

6. The online analysis device for VOCs components in atmospheric particulate matter according to claim 2 is characterized in that: The online analysis equipment also includes: a first buffer chamber and a second buffer chamber, the gas cylinder, the particulate gas source, and the inlet end of the weighing module are commonly connected to the first buffer chamber, and the outlet end of the weighing module, the vacuum pump, and the PTR mass spectrometer are commonly connected to the second buffer chamber.

7. The online analysis device for VOCs components in atmospheric particulate matter according to claim 2 is characterized in that: The electric heating module comprises a heating wire, and the refrigeration module comprises: a multi-layer semiconductor refrigeration sheet, a heat conductor and a capillary stainless steel tube arranged on the multi-layer semiconductor refrigeration sheet, and a ceramic heating block arranged on the heat conductor.

8. The online analysis device for VOCs components in atmospheric particulate matter according to claim 2 is characterized in that: The online analysis equipment also includes a water tank connected to the PTR mass spectrometer.

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