VOC measuring device and method

Abstract

To provide a device and a measurement method which can highly accurately measure a VOC amount generated from a sample under a condition close to an easier and more real use environment.SOLUTION: A measurement device of VOC being a series of devices connecting an air sending pump, an atmospheric pressure regulator, a chamber being a sample container and a VOC measuring instrument via a connecting tube, comprises: the substantially-circular chamber which has a container part and a lid part that can be detachably attached, can be sealed excluding an air sending vent hole and includes a transmission part for irradiating a sample with light between the container part and the lid part; and the atmospheric pressure regulator between the air sending pump and the chamber for making the air in the chamber laminar flow. There is also provided a measurement method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a VOC measuring device and a VOC measuring method. [Background technology]

[0002] In conventional atmospheric chemistry, chemical substances contained in VOCs (volatile organic compounds) that evaporate from objects exposed to the outside air, such as building materials, are analyzed by directly collecting air containing VOCs from near the object into a bag or other container and injecting it directly into a measuring device such as a mass spectrometer, and the amount of VOC emissions is estimated from the analysis results. (See Non-Patent Document 1 (pages 4-5, Figure 1)) However, with this method, only a portion of the air surrounding the object being measured is collected instantaneously, making it unclear whether the air contains volatile VOCs that originate only from the object being measured. It also has problems such as being unable to indicate what proportion of the VOCs emitted from the object being measured over a certain period of time the air collected instantaneously represents, making it impossible to estimate the total amount of VOCs emitted from the object being measured over a certain period of time. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Japan Environmental Measurement and Analysis Association, Air Quality Technology Committee, "Manual for Analysis of Exhaust Gas from Fixed Sources (2021 Edition)", March 15, 2021, p.4-5, 3.27.2 Method of Sampling Sample Gas

[0004] On the other hand, when testing for VOCs emitted from building materials that may be linked to sick house syndrome, the building materials are heated to a specified temperature and stored in a measurement box for a certain period of time, and the gas inside the box is then sampled to directly test for harmful VOCs. Summary of the Invention [Problem to be solved by the invention]

[0005] Previous atmospheric chemistry methods involved directly collecting air containing VOCs around the sample and injecting it into a measuring device such as a mass spectrometer, but the source of the measured VOCs was unclear and the amount of the substance measured could not be considered to be the total amount, so the accuracy was not high.

[0006] On the other hand, when injecting sample air into a measuring device, the air can be agitated during the measurement stage, causing unintended chemical reactions, making it difficult to obtain accurate measurement results. In other words, when the air flowing through the measurement environment is turbulent, the mixing rate of chemical substances is higher than in laminar flow, which can cause chemical reactions between VOCs, resulting in the production of VOCs that are not produced under normal conditions.

[0007] Therefore, rather than injecting air directly into the measuring equipment, the researchers thought that by storing samples such as asphalt to which atmospheric components have been adsorbed in a container, isolating it from outside air while creating a simulated natural environment, and investigating the rate at which VOCs are released from the sample through thermal decomposition and photodecomposition, it would be possible to measure the type and amount of VOCs generated from the sample alone over a certain period of time, and from the measurement results to measure the total amount of VOCs generated from the sample over a long period of time and to estimate the rate at which the sample deteriorates. [Means for solving the problem]

[0008] The gist of the present invention is as follows. (1) VOC measuring equipment The present invention provides a VOC measuring device that has an air pump located upstream of a chamber for storing a sample and a VOC measuring instrument located downstream, and is equipped with a means for irradiating light onto the sample in the chamber, thereby enabling the type and amount of VOCs released from the sample to be measured. The present invention makes it possible to capture and measure VOCs emitted only from a sample under simulated conditions similar to those under natural light, without being affected by external environmental factors such as the intrusion of external air. The present invention also provides a VOC measuring device, in which the chamber is substantially cylindrical, airtight, and has a transmissive portion in part for irradiating light onto a sample stored inside. According to the present invention, VOCs can be released from a sample stored in a chamber under simulated conditions similar to those of natural light, without being influenced by factors outside the measurement device, and the VOC airflow can be prevented from changing in quality before reaching a VOC measuring device downstream. Furthermore, the present invention relates to a VOC measuring device having an air pressure regulator between the air supply pump and the chamber. The present invention prevents the pulsation of the air supply pump from disrupting the airflow of VOCs released from the sample before it reaches the downstream VOC measuring device, thereby preventing unintended chemical reactions and deterioration of the VOCs. (2) VOC analysis method The present invention is a VOC measurement method in which light is irradiated onto a sample inside a chamber from a light irradiation means, air is pumped in from an upstream air pump, and the VOC-mixed air volatilized from the sample in the chamber is measured by a downstream VOC measuring instrument. The present invention makes it possible to capture and measure VOCs released by photolysis from a sample alone under simulated conditions similar to those under natural light, without being affected by external environmental factors. The present invention also provides a VOC measurement method according to claim 4, in which the measurement accuracy is improved by adjusting the air pressure between the air supply pump and the chamber. The present invention prevents the pulsation of the air supply pump from disrupting the airflow of VOCs released from the sample before it reaches the downstream VOC measuring device, thereby preventing unintended chemical reactions and deterioration of the VOCs. Further, the present invention provides a VOC measuring method according to claim 4, wherein the light irradiation means uses a solar simulator that simulates the spectral distribution of sunlight. The present invention makes it possible to capture and measure VOCs emitted only from a sample under simulated conditions similar to those under natural light. Effect of the Invention

[0009] According to the VOC measuring device and measuring method of the present invention, it is possible to accurately measure the type and amount of VOCs released from a sample by photolysis without being affected by the outside air, etc. Furthermore, it is possible to measure the type and amount of VOCs under conditions close to the actual atmospheric environment without causing unintended chemical reactions during the VOC measuring stage. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a layout diagram of the VOC measuring device. [Diagram 2] FIG. [Diagram 3] FIG. 13 is a diagram showing a simulation model of gas in a chamber. [Figure 4] FIG. 1 is a graph showing an example of measurement using a VOC measuring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention will be described with reference to the drawings. 1 is a layout diagram of a VOC measuring device of the present invention. This VOC measuring device 1 comprises an air supply pump 11, a pressure regulator 12, air supply vents 6-7, connecting pipes 8-10, and a chamber 3.

[0012] In FIG. 1, the air supply pump 11 serves to send out clean air 17 through the connecting pipe 10 and to send air into the chamber 3 through the air pressure regulator 12 and the connecting pipe 8. The air pressure regulator 12 is disposed between the air supply pump 11 and the chamber 3 to eliminate the effect of the pulsation of the air supply pump 11 on the measurement. In general, the pulsation of air sent from the air supply pump puts a load on the gas in the downstream chamber and the VOC measuring instrument, and tends to disturb the downstream air flow. Therefore, by passing the clean air 17 sent from the air supply pump 11 through the air pressure regulator 12 with two outlets on the downstream side, it is possible to prevent the air from being sent to the VOC measuring instrument 2 under a load, and to send out air in accordance with the flow rate of the intake pump that takes in air built into the VOC measuring instrument 2, thereby playing a role in maintaining a constant flow rate of air in the chamber 3.

[0013] In Fig. 1, the VOC measuring instrument 2 is a mass spectrometer such as PTR-Tof-MS that uses a soft ionization method in which molecules are ionized by protonation and the protonated ions are detected, and is a device that measures the VOC-mixed air 18 that has passed through the chamber 3. It is desirable to adopt an instrument that is equipped with the conditions to analyze as many types of VOCs as possible at once.

[0014] The chamber 3 is a roughly circular metal container made of stainless steel or other material, as shown in Figure 2, and has a cavity inside in which a sample can be stored. In order to keep the gas flowing inside the chamber 3 in a laminar flow state, it is difficult to maintain the gas in a laminar flow state in a roughly rectangular shape, so the roughly circular shape is desirable. In addition, Teflon is applied to the inside of the chamber 3 to prevent contamination from oil adhering to the stainless steel or other material. (Registered Trademark)The chamber 3 is coated with a coating. Furthermore, the chamber 3 has a detachable lid 4. Meanwhile, in order to irradiate the sample 14 inside the chamber 3 with light, the lid 4 is provided with a transparent section 15 made of quartz glass, and light from the light irradiation means is taken in from outside the chamber 3. The material of the transparent section 15 is preferably quartz glass, since it transmits light with ultraviolet wavelengths, but calcium fluoride, barium fluoride windows, etc. can also be used as window materials that transmit ultraviolet wavelengths. In addition, a light irradiation means may be provided inside the chamber 3 as a method of irradiating light to the sample 14 inside the chamber 3. The connection parts of the vents 6 and 7 of the chamber 3 use NPT threads 19 to prevent gas leakage. When light is irradiated from the light irradiation means 16 onto the sample 14 in the chamber 3, the VOCs 13 volatilized from the sample 14 are mixed with the clean air 17 flowing into the chamber 3 from the connecting pipe 8 to become VOC-mixed air 18, which reaches the VOC measuring instrument 2 through the connecting pipe 9.

[0015] In FIG. 1, the connecting pipes 8, 9, and 10 are made of Teflon to prevent contamination from oil contained in gas, etc. (Registered Trademark) The pipe is formed from the material.

[0016] In FIG. 1, light irradiating means 16 is a means for irradiating a sample with light to promote photodecomposition of the sample. By using a solar simulator that simulates the spectral distribution of sunlight rather than a specific single wavelength for the light irradiation means 16, it is possible to reproduce the photochemical oxidation reaction and photodecomposition of aerosols under conditions closer to the actual atmospheric environment. In addition, the light irradiation means 16 may be a method in which the light irradiation means 16 illuminates the inside of the chamber 3 from the outside of the chamber 3 provided with the transmission part 15, or a method in which the light irradiation means 16 is provided inside the chamber 3.

[0017] Based on Figure 1, the procedure for actually measuring the VOC content of a sample will be explained. (1) The sample 14 is placed in the container portion within the chamber 3. (2) The lid portion 4 and the container portion 5 of the chamber 3 are joined together and sealed with the bolt screws 19. (3) The air supply pump 11, the air pressure regulator 12, the air supply vents 6 to 7, the connecting pipes 8 to 10, the chamber 3, and the VOC measuring device 2 are arranged and connected. (4) The standard gas is fed from the gas supply pump 11, and the VOC concentration in the chamber 3 is allowed to stabilize. (5) When the increase in VOC concentration has subsided, light is irradiated from the light irradiation means 16 consisting of a solar simulator toward the transmitting portion 15 of the chamber 3 with a wavelength of 300 to 1,100 W / m2 as a reference, and the light is irradiated onto the sample 14. (6) After irradiating light for about 3 hours, turn off the light irradiation means 16. (7) Wait again until the VOC concentration stabilizes. (8) Measure the amount of VOCs using VOC meter 2. EXAMPLES

[0018] An experiment was conducted using the measuring device and measuring method according to the present invention, using an asphalt sample collected from a roadside. In this experiment, an asphalt sample was placed in a container 5, and a stainless steel chamber 3 was sealed with a lid including a quartz glass plate in part. A simulated sunlight light was irradiated as a light irradiation means 16 onto the asphalt sample, and the VOCs generated by photolysis from the sample were measured by a VOC measuring device 2. To confirm the generation of VOCs due to photochemical reactions on the sample surface, the experiment investigated the differences in ion mass distribution (mass spectrum) in four stages, as shown in the upper left graph in Figure 4. Stable state 1: After the sample is stored in the chamber 3, the air supply pump 11 starts supplying air, measurement is started by the VOC measuring instrument 2 (PTR-Tof-MS), and air supply is continued until the VOC concentration stabilizes. During heating: In order to distinguish between photoreaction and volatilization of VOCs due to an increase in the sample surface temperature, the sample was heated to about 60-70°C using infrared light. When irradiated with light: The stage when the light irradiation means 16 (simulated sunlight light) is turned on and a photochemical reaction occurs Stable stage 2: When the rate of increase in VOC concentration due to photoreaction slows down, turn off the simulated sunlight light and wait until the VOC concentration drops and stabilizes.

[0019] The graph in the upper left of Figure 4 shows the volume concentration (Concentration (ppbv)) of formaldehyde at each stage. On the other hand, in order to understand the increase or decrease in the "type" of VOC, the m / s intensity ratio (intensity) at each stage was calculated and shown in Figures 4-1 to 4-3 in Figure 4. Note that each figure showing the spectrum in Figures 4-1 to 4-3 in Figure 4 is an enlarged view, and by taking the (heated) / (stable 1) ratio and the (light irradiation) / (heated) ratio for the asphalt sample, the distribution of the mass-to-charge ratio (m / z value) of VOCs released by volatilization due to the rise in surface temperature and VOCs released by photoreaction and their increase ratio are shown. When heated, VOCs with m / z values ​​of 30 or less and 500 or more increased significantly compared to when stable, but the intensity ratio of VOCs with m / z values ​​of 40 to 300 increased only by about 1 to 3 times on average (Figure 4-2). On the other hand, the change in the mass spectrum when heated under light irradiation showed a remarkable increase in concentration, with the intensity of VOCs with m / z values ​​of 40 to 300 being up to 25 times higher (Figure 4-3). This shows that the VOC measurement method implemented by the device of the present invention can measure a wide variety of VOCs, from low to high molecular weight, caused by photochemical reactions, compared to the method of measuring VOCs volatilized from a sample under room temperature or heated conditions.

[0020] In addition, the results of a simulation of the gas flowing inside the chamber of this device using the mathematical modeling software COMSOL Multiphysics are shown in Figure 3. Since no swirling air currents were observed, it can be seen that the gas flow was in a laminar state inside the chamber during the experiment. [Explanation of symbols]

[0021] 1 VOC measuring device 2 VOC measuring device 3. Chamber 4 Lid 5 Container section 6 Ventilation holes 7. Ventilation 8 Connecting Pipe 9 Connecting Pipe 10 Connecting pipe 11 Air supply pump 12 Pressure Regulator 13 VOC 14 Samples 15 Transparent part 16 Light irradiation means 17 Clean Air 18 VOC mixed air 19 Screws

Claims

1. A VOC measuring device capable of measuring the type and amount of VOCs generated from a sample, comprising an air supply pump arranged upstream of a chamber for storing a sample and a VOC measuring device arranged downstream, a means for irradiating light onto the sample in the chamber, and an air pressure regulator between the air supply pump and the chamber.

2. 2. The VOC measuring device according to claim 1, wherein the chamber is substantially cylindrical, airtight, and has a transmissive portion in part for irradiating light onto a sample stored inside.

3. A VOC measurement method comprising: irradiating a sample inside a chamber with light from a light irradiation means; feeding air from an upstream air pump; adjusting the air pressure between the air pump and the chamber; and measuring the VOC-mixed air volatilized from the sample in the chamber with a downstream VOC measuring device.

4. 4. The VOC measuring method according to claim 3, wherein the light irradiation means uses a solar simulator that simulates the spectral distribution of sunlight.

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