JP2017122661A - Volatile organic compound measuring device and volatile organic compound measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a volatile organic compound measuring device and a volatile organic compound measuring method that can measure a low level of volatile organic compound in an environmental atmosphere.SOLUTION: The VOC in an environmental atmosphere is concentrated by a concentration column 3, desorption of the concentrated VOC from the concentration column 3 is promoted by heating of a heater 4, and a high level of VOC is oxidized so that a high level of carbon dioxide is generated and is measured by an NDIR measuring unit 13. Since the measuring subject is contained in a high concentration, the subject can be measured by the NDIR measuring unit 13 and a VOC containing oxygenated hydrocarbon can be measured.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a volatile organic compound measuring apparatus and a volatile organic compound measuring method for measuring the amount of a volatile organic compound in the ambient air.

  In order to prevent air pollution, the amount of volatile organic compounds discharged into the atmosphere from chemical product manufacturing plants and the like is suppressed by legal regulations and voluntary regulations. In order to suppress the emission amount, it is necessary to quantitatively measure how much volatile organic compounds are emitted, and the measurement is mainly performed in a plant facility which is an emission source.

  Examples of the method for measuring volatile organic compounds include the FID method (hydrogen flame ionization method), the NDIR method (non-dispersive infrared absorption method), and the PID method (photoionization detection method). For example, Patent Document 1 describes a volatile organic compound measuring apparatus using the NDIR method.

JP 2008-261865 A

  For the purpose of preventing air pollution, it is important to measure not only the amount of volatile organic compounds in the emission source of volatile organic compounds but also the amount of volatile organic compounds in the ambient air. However, since the amount of volatile organic compounds in the ambient air is extremely small compared to the emission source, measurement is difficult. The volatile organic compound measuring apparatus described in Patent Document 1 adopting the NDIR method is not suitable for measuring the amount of volatile organic compounds in the ambient air because it has low sensitivity and low measurement accuracy in a low concentration range. The FID method can measure a low concentration range, but cannot measure oxygenated hydrocarbons and cannot measure the total amount. The PID method is also selective for volatile organic compounds and can only measure specific compounds.

  The objective of this invention is providing the volatile organic compound measuring apparatus and volatile organic compound measuring method which can measure the low concentration volatile organic compound contained in environmental atmosphere.

The present invention is a volatile organic compound measuring device for measuring the amount of volatile organic compounds containing oxygenated hydrocarbons contained in the atmospheric air,
An air intake section for taking in the atmospheric air;
A concentration column for adsorbing and concentrating volatile organic compounds contained in the air taken in by the air take-in part;
A desorption promoting part that promotes desorption of the concentrated volatile organic compound from the concentration column;
A catalytic oxidation unit that oxidizes a volatile organic compound desorbed from the concentration column in the presence of an oxidation catalyst to generate carbon dioxide;
A volatile organic compound measuring device comprising: an output unit that measures the amount of carbon dioxide generated in the catalytic oxidation unit by a non-dispersive infrared absorption method and outputs a volatile organic compound amount in terms of carbon is there.

  Further, the present invention is characterized in that the desorption promoting unit heats the concentration column to promote desorption of a volatile organic compound from the concentration column.

  In the invention, it is preferable that the desorption promoting unit includes a cooling unit that cools the concentration column after the concentration column is heated and the volatile organic compound is desorbed from the concentration column.

The present invention also includes a zero gas generation unit that generates zero gas from which carbon dioxide and moisture have been removed from the air taken in by the air intake unit,
The concentration column is washed by allowing the zero gas generated in the zero gas generation unit to flow through the concentration column.

The present invention is also a volatile organic compound measuring method for measuring the amount of volatile organic compounds containing oxygenated hydrocarbons contained in the atmospheric air,
An air intake process for capturing environmental air;
A concentration step in which volatile organic compounds contained in the taken-in air are adsorbed on a concentration column and concentrated;
A desorption step of desorbing the concentrated volatile organic compound from the concentration column, wherein the desorption step promotes desorption;
A catalytic oxidation step in which desorbed volatile organic compounds are oxidized in the presence of an oxidation catalyst to generate carbon dioxide;
An output step of measuring the amount of generated carbon dioxide by a non-dispersive infrared absorption method and outputting the amount of a volatile organic compound in terms of carbon, and a method for measuring a volatile organic compound.

  According to the present invention, there is provided a volatile organic compound measuring device that measures the amount of volatile organic compounds including oxygen-containing hydrocarbons contained in the environmental atmosphere, and when the atmospheric intake unit takes in the environmental air, the concentration column is The volatile organic compound contained in the atmosphere taken in by the atmosphere taking-in part is adsorbed and concentrated. The desorption promoting unit promotes desorption of the concentrated volatile organic compound from the concentration column. The catalytic oxidation unit oxidizes the volatile organic compound desorbed from the concentration column in the presence of an oxidation catalyst to generate carbon dioxide, and the output unit non-disperses the amount of carbon dioxide generated in the catalytic oxidation unit Measured by the infrared absorption method and output the amount of volatile organic compounds in terms of carbon.

  Since the volatile organic compound containing the oxygen-containing hydrocarbon is concentrated and measured by the non-dispersive infrared absorption method, it is possible to measure a low concentration volatile organic compound contained in the ambient air.

  Further, according to the present invention, desorption of volatile organic compounds from the concentration column can be easily promoted by heating.

  Moreover, according to this invention, by providing the cooling part which cools a concentration column, time until an apparatus becomes a state which can be measured next can be shortened, and the measurement frequency in one day can be raised.

  Further, according to the present invention, the zero gas generation unit generates zero gas from which carbon dioxide and moisture are removed from the atmosphere taken in by the atmospheric intake unit, and the zero gas is allowed to flow through the concentration column to cause the concentration column to flow. Wash.

  Since zero gas is generated in the apparatus, it is not necessary to introduce zero gas from the outside.

  Further, according to the present invention, there is provided a volatile organic compound measuring method for measuring the amount of volatile organic compounds containing oxygenated hydrocarbons contained in the environmental atmosphere, and the concentration step is performed when the atmospheric air is taken in the atmospheric taking step. Then, the volatile organic compound contained in the taken-in air is adsorbed on the concentration column and concentrated. In the desorption step, the concentrated volatile organic compound is desorbed from the concentration column. At this time, desorption from the concentration column is promoted. In the catalytic oxidation process, desorbed volatile organic compounds are oxidized in the presence of an oxidation catalyst to generate carbon dioxide, and in the output process, the amount of generated carbon dioxide is measured by a non-dispersive infrared absorption method. Output the amount of volatile organic compound in terms of conversion.

  Since the volatile organic compound containing the oxygen-containing hydrocarbon is concentrated and measured by the non-dispersive infrared absorption method, it is possible to measure a low concentration volatile organic compound contained in the ambient air.

It is a figure which shows the structure of the volatile organic compound measuring apparatus 1 which is embodiment of this invention. It is a flowchart which shows the process of the volatile organic compound measuring method of this invention. It is a figure for demonstrating operation | movement of the VOC measuring apparatus 1 in the sampling process of step S2. It is a figure for demonstrating operation | movement of the VOC measuring apparatus 1 in the cleaning process of step S3. It is a figure for demonstrating operation | movement of the VOC measuring apparatus 1 in the 1st backflush process of step S4. It is a graph which shows the measurement result of a hydrocarbon compound. It is a graph which shows the measurement result of a hydrocarbon compound. It is a figure for demonstrating the structure in 1 A of VOC measuring apparatuses which are other embodiment of this invention, and the operation | movement in a sampling process. It is a figure which shows operation | movement. It is a figure for demonstrating operation | movement of 1 V of VOC measuring apparatuses in a cleaning process. It is a figure for demonstrating operation | movement of 1 A of VOC measuring apparatuses in a 1st back flush process.

  FIG. 1 is a diagram showing a configuration of a volatile organic compound measuring apparatus 1 according to an embodiment of the present invention. A volatile organic compound measuring device (hereinafter referred to as “VOC measuring device”) 1 includes a filter 2, a concentration column 3, a heater 4, a cooling fan 5, a mass flow controller 6, an air pump 7, a first oxidation catalyst column 8, A carbon dioxide absorber 9, a first semipermeable membrane dehumidifier 10, a second oxidation catalyst column 11, a second semipermeable membrane dehumidifier 12 and an NDIR measuring device 13 are provided. The VOC measurement device 1 also includes switching valves V1 to V8 that switch between a plurality of pipes that connect the respective parts and the open / closed state of the pipe flow path.

  The VOC measuring device 1 of the present invention is a measuring device that measures volatile organic compounds (VOC) contained in the ambient air, and is particularly a measuring device suitable for measuring VOCs containing low concentrations and oxygenated hydrocarbons. is there.

  The filter 2 passes the ambient air taken into the apparatus and collects particulate matter contained in the ambient air. As the filter 2, for example, tetrafluoroethylene resin can be used. The concentration column 3 adsorbs and concentrates the VOC containing low concentration and oxygenated hydrocarbons contained in the taken-in air. Specifically, an adsorption-type filler or a porous polymer is packed in the column as an adsorbent, and the VOC is adsorbed on the adsorbent by continuously passing air through the column. Examples of the concentration column 3 used in the VOC measurement device 1 of the present invention include MS3A, MS4A, MS13X, TenaxTA, TenaxGR, PorapakS, and PorapakQ manufactured by GL Sciences. The capacity of the concentration column 3 is, for example, 5 to 50 cc.

  The heater 4 accelerates the desorption of the concentrated VOC adsorbed by the adsorbent of the concentration column 3 from the concentration column 3 and heats the concentration column 3 to desorb the concentration column 3 in a short time. The separation promotion part. The VOC measuring device 1 of the present invention measures the concentration of VOC by the NDIR measuring device 13 provided at the most downstream side of the device.

  Since the NDIR measuring instrument 13 is low in sensitivity to low concentration VOC and inferior in measurement accuracy, the concentration column 3 attempts to concentrate the low concentration VOC in the ambient atmosphere. By being able to measure with the NDIR measuring instrument 13, the FID method can also measure oxygen-containing hydrocarbons that cannot be measured.

  However, when the VOC concentrated by the concentration column 3 is desorbed and sent out to the NDIR measuring device 13, if the VOC gradually flows out from the concentration column 3, the NDIR measuring device 13 eventually measures a low concentration VOC. As a result, the meaning of concentration disappears. Therefore, in the present invention, a desorption promoting unit is provided so that the VOCs adsorbed and concentrated on the concentration column 3 are desorbed from the concentration column 3 and flow out in a short time. When the desorption promoting part accelerates the desorption of VOC from the concentration column 3, the VOC desorbs and flows out in a short time, and the high concentration VOC reaches the NDIR measuring instrument 13, so that it can be measured. Become.

  The heating conditions by the heater 4 or other heating means may be appropriately set according to the type of adsorbent packed in the concentration column 3 to be used. When Porapak is used as the adsorbent, the concentration column 3 is For example, what is necessary is just to heat to 50-150 degreeC. As long as it can be heated in such a temperature range, any heating method may be used, a heating material such as a metal wire is wound around the concentration column 3 and heated, the concentration column 3 is covered with a jacket, A method of heating by flowing a heating medium in the jacket, a method of heating the concentrating column 3 by blowing hot air, and the like can be used.

  The cooling fan 5 is a cooling unit that cools the concentration column 3 heated by the heater 4. Since the heating of the concentration column 3 by the heater 4 promotes the desorption of VOC as described above, when the temperature is increased by the heating of the heater 4, the taken-in air flows through the concentration column 3. Even if it is made, VOC is not adsorbed to the concentration column 3. In order to start the next measurement, it is necessary to wait until the concentration column 3 is lowered to a temperature at which VOC can be adsorbed. The concentration column 3 may be naturally cooled, but in that case, cooling takes time. By forcibly cooling the concentration column 3 using the cooling fan 5, the temperature can be lowered to a temperature at which VOC can be adsorbed in a short time, and the start of the next measurement can be accelerated.

  The mass flow controller 6 measures the ambient air intake flow rate on the basis of mass and controls the air pump 7 so as to obtain a preset mass flow rate. The air pump 7 is a gas suction pump for sucking and taking in atmospheric air into the apparatus. For example, an existing pump such as a diaphragm type, a bellows type, or an electromagnetic type can be used. The mass flow rate controlled by the mass flow control device 6 is, for example, in the range of 100 to 1000 mL / min.

  The first oxidation catalyst column 8 is a column for oxidizing the VOC contained in the atmosphere that has not passed through the concentration column 3 to generate carbon dioxide, and is filled with an oxidation catalyst. When the VOC flows through the first oxidation catalyst column 8, it is oxidized by the action of the oxidation catalyst to generate carbon dioxide. As the oxidation catalyst, a catalyst in which a noble metal catalyst such as platinum, palladium or rhodium is supported on a metal oxide carrier such as alumina or ceria can be used. The first oxidation catalyst column 8 may be heated in order to further promote the oxidation reaction of VOC by the oxidation catalyst.

  The carbon dioxide absorber 9 absorbs and removes carbon dioxide originally contained in the atmosphere and carbon dioxide generated by oxidizing the VOC in the first oxidation catalyst column 8.

  The first semipermeable membrane dehumidifier 10 removes moisture contained in the taken-in ambient air in order to generate zero gas. In the present embodiment, a tube-type dehumidifier using a semipermeable membrane is used. However, the present invention is not limited to this, as long as it can remove moisture contained in the captured air.

  The 1st oxidation catalyst column 8, the carbon dioxide absorber 9, and the carbon dioxide absorber 9 comprise a zero gas production | generation part.

  The second oxidation catalyst column 11 is a column for generating carbon dioxide by oxidizing the VOC that has been concentrated by the concentration column 3 and then desorbed, and is filled with an oxidation catalyst. When the VOC flows through the first oxidation catalyst column 8, it is oxidized by the action of the oxidation catalyst to generate carbon dioxide. As the oxidation catalyst, a catalyst in which a noble metal catalyst such as platinum, palladium or rhodium is supported on a metal oxide carrier such as alumina or ceria can be used. The first oxidation catalyst column 8 may be heated in order to further promote the oxidation reaction of VOC by the oxidation catalyst.

  The second semipermeable membrane dehumidifier 12 removes moisture from the atmosphere in order to suppress the influence of moisture contained in the captured ambient atmosphere on the measurement result. In the present embodiment, a tube-type dehumidifier using a semipermeable membrane is used. However, the present invention is not limited to this, as long as it can remove moisture contained in the captured air.

  The NDIR measuring instrument 13 is a measuring instrument that measures the amount of carbon dioxide by a non-dispersive infrared absorption method. The concentrated VOC containing oxygen-containing hydrocarbons is oxidized by the second oxidation catalyst column 11 to generate carbon dioxide. The amount of generated carbon dioxide is measured by the NDIR measuring device 13. If it is considered that the total amount of VOC has changed to carbon dioxide due to the oxidation reaction, the amount of carbon dioxide measured by the NDIR measuring device 13 correlates with the amount of VOC. Therefore, the measurement result of the NDIR measuring device 13 is VOC in terms of carbon. Represents quantity.

  FIG. 2 is a flowchart showing the steps of the volatile organic compound measurement method (hereinafter referred to as “VOC measurement method”) of the present invention. The VOC measurement method is performed using the VOC measurement apparatus 1.

  When the power source of the VOC measurement device 1 is turned on, a measurement flow is started. In step S1, the measurement waits for the purpose of stabilizing the operation of each part of the VOC measurement device 1. The waiting time may be set to about several minutes, and is, for example, 1 minute in this embodiment.

  When the set waiting time has elapsed, in the sampling process of step S2, the ambient atmosphere is taken in, and the taken-in atmosphere is passed through the concentration column 3 to concentrate VOC contained in the atmosphere. The sampling process includes an air intake process and a concentration process.

  FIG. 3 is a diagram for explaining the operation of the VOC measurement device 1 in the sampling process of step S2. In FIG. 3, among the pipes of the VOC measurement device 1, those indicated by thick solid lines are flow paths through which gas flows, and those indicated by broken lines are flow paths through which gas does not flow. Also, in FIG. 3, each valve with the left half painted black is in a closed state, and each valve painted with white is in an open state. About these description, it is the same also about the following FIG. 4 and FIG.

  In the sampling process, the atmospheric air is taken in at a constant flow rate by the operation of the mass flow controller 6 and the air pump 7, and the taken-in air passes through the filter 2 and the concentration column 3, passes through the first oxidation catalyst column 8, The carbon dioxide absorber 9, the first semipermeable membrane dehumidifier 10, the second oxidation catalyst column 11, the second semipermeable membrane dehumidifier 12 and the NDIR measuring device 13 are passed through and exhausted outside the apparatus. The atmosphere continuously taken in at a constant flow rate continuously flows through the concentration column 3, and VOC contained in the atmosphere is adsorbed on the concentration column 3 and concentrated.

  In the sampling process, the heater 4 and the cooling fan 5 are not operated, and the valves V3, V4, V5, V6, and V7 are not operated. The pump 7, the first oxidation catalyst column 8, the carbon dioxide absorber 9, the first semipermeable membrane dehumidifier 10, the second semipermeable membrane dehumidifier 12, the NDIR measuring device 13 and the concentration by operating V1, V2 and V8. The ambient air is passed through column 3.

  The sampling process is performed for several tens of minutes in order to concentrate the VOC in the concentration column 3. In this embodiment, for example, 18 minutes.

  When the sampling process is completed, a cleaning process is performed next. In the cleaning step, zero gas obtained by removing carbon dioxide and moisture is generated, and cleaning is performed by flowing the generated zero gas through the concentration column 3.

  FIG. 4 is a diagram for explaining the operation of the VOC measurement device 1 in the cleaning process of step S3.

  In the cleaning process, the mass air flow control device 6 and the air pump 7 are operated so that the ambient air is taken in at a constant flow rate, and the taken-in air operates without passing through the filter 2 and the concentration column 3. Through the first oxidation catalyst column 8, the carbon dioxide absorber 9 and the first semipermeable membrane dehumidifier 10, zero gas is generated. The generated zero gas is allowed to flow through the concentration column 3, and is passed through the second oxidation catalyst column 11, the second semipermeable membrane dehumidifier 12 and the NDIR measuring device 13 and exhausted outside the apparatus. The concentration column 3 is washed by allowing zero gas to flow through the concentration column 3.

  In the cleaning process, the heater 4 and the cooling fan 5 are not operated, and the valves V1, V2, V4, V6, and V7 are not operated. By operating the valves V3, V7, V5, the first oxidation catalyst column 8, the carbon dioxide absorber 9, the first semipermeable membrane dehumidifier 10, the second oxidation catalyst column 11, the second semipermeable membrane dehumidifier 12 and The NDIR measuring device 13 is operated to pass the ambient air, and zero gas is generated from the taken air.

  The cleaning process is performed for several minutes to wash the concentration column 3. In this embodiment, it is 2 minutes, for example.

  When the cleaning process is completed, a first backflush process is performed next. In the first backslash step, the VOC concentrated by flowing a carrier gas through the concentration column 3 in the opposite direction to the sampling step is desorbed from the concentration column 3 and flows out.

  FIG. 5 is a diagram for explaining the operation of the VOC measurement device 1 in the first backflushing process of step S4.

  In the first backflush process, the atmospheric air is taken in at a constant flow rate by the operation of the mass flow controller 6 and the air pump 7, and the taken-in air passes through the filter 2 and does not pass through the concentration column 3, A carrier gas (zero gas) is generated through the operating first oxidation catalyst column 8, carbon dioxide absorber 9 and first semipermeable membrane dehumidifier 10. On the other hand, the heater 4 is operated to heat the concentration column 3, and the desorption of the concentrated VOC is promoted so that the carrier gas flows through the concentration column 3. A high concentration of VOC can be caused to flow out of the concentration column 3 by the carrier gas. When a carrier gas containing a high concentration of VOC flows into the second oxidation catalyst column 11, the VOC is oxidized and carbon dioxide is generated. The generated carrier gas containing carbon dioxide has its moisture removed through the second semipermeable membrane dehumidifier 12, the amount of carbon dioxide is measured by the NDIR measuring device 13, and is exhausted outside the apparatus.

  In the first backflush process, the cooling fan 5 is not operated, and the valves V1, V2, V5, V7, and V8 are not operated. The heater 4 is operated to heat the concentration column 3, the valves V3, V6, and V4 are operated, and the first oxidation catalyst column 8, the carbon dioxide absorber 9, and the first semipermeable membrane dehumidifier 10 are operated. Pass air through to generate carrier gas. The generated carrier gas is allowed to flow through the heated concentration column 3, and the second carrier catalyst column 11 and the second semipermeable membrane dehumidifier 12 operating the concentrated carrier gas containing high-concentration VOC are operated. And it passes through the NDIR measuring device 13 and the amount of carbon dioxide is measured.

  The first backflush process is performed for several minutes in order to allow VOC to flow out of the concentration column 3 in a short time. In this embodiment, it is 4 minutes, for example.

  When the first backflush process is completed, a second backflush process is performed next. In the second backslash step, the carrier gas is allowed to flow through the concentration column 3 in the opposite direction to the sampling step in the same manner as in the first backflush, and the concentration column 3 is cooled by the cooling fan 5.

  The operation of the VOC measurement device 1 in the second backflush process in step S5 is the same as that in FIG.

  In the second backflush process, the atmospheric air is taken in at a constant flow rate by the operation of the mass flow controller 6 and the air pump 7, and the taken-in air passes through the filter 2 and does not pass through the concentration column 3, Carrier gas is generated through the operating first oxidation catalyst column 8, carbon dioxide absorber 9 and first semipermeable membrane dehumidifier 10. The generated carrier gas is allowed to flow through the concentration column 3 and the cooling fan 5 is operated to cool the concentration column 3. The carrier gas that has flowed through the concentration column 3 passes through the second oxidation catalyst column 11, the second semipermeable membrane dehumidifier 12, and the NDIR measurement device 13 that are not in operation, and is exhausted outside the apparatus.

  In the second backflushing process, the heater 4 is not operated, and the valves V1, V2, V5, V7, and V8 are not operated. By operating the cooling fan 5 to cool the concentration column 3 and operating the VOC1 oxidation catalyst column 8, the carbon dioxide absorber 9 and the first semipermeable membrane dehumidifier 10, carrier gas is generated from the air taken in. The produced carrier gas is allowed to flow through the cooling concentration column 3 and is passed through the second oxidation catalyst column 11, the second semipermeable membrane dehumidifier 12 and the NDIR measuring device 13 which are not operating.

  The second backflushing process is performed for several minutes to cool the concentration column 3. In this embodiment, it is 5 minutes, for example.

  In step S6, a VOC output process is performed. In the VOC output step, a VOC amount in terms of carbon is output based on the amount of carbon dioxide measured by the NDIR measuring device 13 in the first backflush step. The VOC output process does not need to be performed after the second backflush process, and is performed at the same time as the first backflush process, that is, the amount of carbon dioxide is measured by the NDIR measuring instrument 13 in the first backflush process and is converted into carbon. The amount of VOC may be output. Further, after the first backflushing process, it may be performed simultaneously with the second backflushing process, that is, while the concentration column 3 is cooled, the carbon-converted VOC amount may be output.

  As described above, according to the present invention, VOCs in the ambient air are concentrated by the concentration column 3, the desorption of the concentrated VOCs from the concentration column 3 is promoted, and the high concentration VOC is oxidized to form a high concentration carbon dioxide. Is generated and measured with an NDIR measuring instrument. Since the measurement object has a high concentration, it can be measured with an NDIR measuring instrument, and further, VOC containing oxygen-containing hydrocarbons can be measured.

(Example)
A plurality of hydrocarbon compounds were measured using the VOC measuring device 1 of the present invention. For comparison, the same hydrocarbon compound was measured using a non-methane hydrocarbon meter using the FID method.

  The VOC measurement device 1 was measured with a 30-minute cycle, and the measurement conditions of the non-methane hydrocarbon meter were measured with a 6-minute cycle. The VOC measurement apparatus 1 sampled by sampling 9000 mL of air at a flow rate of 500 mL / min for 18 minutes. The cleaning process was 4 minutes, the first backflush process was 4 minutes, the second backflush process was 2 minutes, and the waiting time was 2 minutes.

  The hydrocarbon compounds to be measured were maleic anhydride, toluene, citraconic anhydride, formaldehyde, and methylglyoxal.

  6 and 7 are graphs showing measurement results of hydrocarbon compounds. FIG. 6 shows the measurement results of maleic anhydride and toluene, and FIG. 7 shows the measurement results of citraconic anhydride, formaldehyde, and methylglyoxal. 6 and 7, the left side is the measurement result of the VOC measurement device 1 of the present invention, and the right side is the measurement result of the non-methane hydrocarbon meter.

  As for toluene and methylglyoxal, a peak indicating a hydrocarbon compound is observed in both the measurement results of the present invention and the non-methane hydrocarbon meter, indicating that measurement is possible.

  For maleic anhydride, citraconic anhydride and formaldehyde, the non-methane hydrocarbon meter does not show a peak indicating a hydrocarbon compound, and oxygenated hydrocarbons such as maleic anhydride, citraconic anhydride and formaldehyde are measured. I understand that I can't. On the other hand, in the measurement result of the present invention, a peak indicating a hydrocarbon compound is observed, and it can be seen that oxygen-containing hydrocarbons such as maleic anhydride, citraconic anhydride and formaldehyde can also be measured.

Table 1 shows the measurement results of the amount of yield and yield of a plurality of hydrocarbon compounds.

The yield was measured and calculated as follows.
Put the hydrocarbon compound in a dish or bee, put it in a water bath or sand tub, and ventilate the zero gas with a gas flow rate V1 (L / min) to sublimate or vaporize the hydrocarbon compound. A gas containing is generated. Since the hydrocarbon compound generated at this time has a relatively high concentration, the column concentration is omitted, the oxidation catalyst column and the dehumidifier are passed through as they are, the VOC concentration is measured with an NDIR measuring instrument, and C1 (gC / L) and To do. The low concentration hydrocarbon compound is diluted with a large amount of cellogas V2 (L / min) with respect to the relatively high concentration VOC gas generated above. The generation concentration C2 (gC / L) when diluted is calculated by the following formula.
C2 = C1 × V1 / (V1 + V2)
From the gas flow rate V3 (L / min) passing through the column and the time T (min), the carbon amount CA (g) of the hydrocarbon compound passing through the column is calculated by the following equation.
CA = T × C2 × V3
If the flow rate NDIR measuring device (L / min) passing through the NDIR measuring device with the output C3 (gC / L) of the NDIR measuring device is integrated with the peak appearance time, the carbon amount CA ′ passing through the NDIR measuring device is Calculated by the following formula.
CA ′ = ∫ (C3) (V3) dt
Based on the obtained CA and CA ′, the yield (%) is calculated by the following formula.
Yield (%) = CA ′ / CA × 100
As shown in Table 2, the evaluation of the yield is shown in Table 1 with symbols corresponding to the measurement results.

In order to evaluate the measurement sensitivity of the VOC measurement device 1 of the present invention, the detection limit was estimated using a value three times the standard deviation using zero gas that does not contain hydrocarbons. The detection limit of the VOC measurement device 1 was 8.4 ppbC, and the detection limit for non-methane hydrocarbons was about 10 ppbC. Usually, since the detection limit of a VOC detector that detects CO ₂ using an NDIR measuring instrument without concentration by a column is about 500 ppbC, it can be seen that the sensitivity of the VOC measuring device 1 of the present invention is extremely high. . Thus, the measurement sensitivity of the VOC measurement device 1 of the present invention is high due to the concentration of VOC in the concentration column.

It is estimated that most of the VOC is desorbed from the concentration column in about 30 seconds out of the 4 minutes of the first backflush process at a sampling time of 18 minutes, and concentration is performed 30 to 40 times from the elution time. . Therefore, for a plurality of hydrocarbon compounds, the apparent concentration is calculated according to the following formula from the average carbon concentration output within a half-width time that is ½ of the peak value of eluted CO ₂ and the generated average concentration. Magnification was calculated.
Apparent concentration ratio = A / B
Here, A is the average carbon concentration output within the half-width time, and B is the generated average carbon concentration. The results are shown in Table 3.

  As shown in Table 3, it was found that the VOC measurement device 1 of the present invention can be measured with high sensitivity by column concentration. It has been found that the VOC measurement apparatus 1 of the present invention can measure a concentration that cannot be detected by simply combining the NDIR measuring instrument and the catalyst column. Note that the concentration ratio varies depending on the type of compound. The appearance of a peak differs in the first backflush process, and the apparent concentration ratio of a substance eluted at a stretch increases with the recovery rate.

  Next, another embodiment of the present invention will be described. FIGS. 8-10 is a figure which shows the structure of 1 A of VOC measuring apparatuses which are other embodiment of this invention, and. In the present embodiment, a three-way switching valve V9 is provided between the second oxidation catalyst column 11 and the second semipermeable membrane dehumidifier 12, and a flow path that bypasses the second oxidation catalyst column 11 is provided. 1 is the same as the VOC measurement apparatus 1 of the embodiment shown in FIG. 1, and the other configurations are the same.

  The gas that has passed through the first semipermeable membrane dehumidifier 10 can be switched between the case of passing through the second oxidation catalyst column 11 and the case of not passing through the three-way switching valve V9. In the sampling process, the cleaning process, and the first backflush process, the VOC measurement device 1A can be operated so as not to pass through the second oxidation catalyst column 11.

When the second oxidation catalyst column 11 is not passed, the VOC concentrated by the concentration column 3 is not oxidized through the sampling process, the cleaning process, and the first backflush process, so that CO ₂ is not generated, and the NDIR measuring instrument 13 Not measured. As a result, so-called zero-based measurement can be performed. In the VOC measurement device 1A of the present embodiment, the zero base measurement is performed under almost the same conditions as the sample measurement because it is the same as the sample measurement except that the second oxidation catalyst column 11 is not passed during the zero base measurement. Can do.

1,1A Volatile Organic Compound Measuring Device (VOC Measuring Device)
DESCRIPTION OF SYMBOLS 2 Filter 3 Concentration column 4 Heating heater 5 Cooling fan 6 Mass flow controller 7 Air pump 8 1st oxidation catalyst column 9 Carbon dioxide absorber 10 1st semipermeable membrane dehumidifier 11 2nd oxidation catalyst column 12 2nd semipermeable membrane dehumidification 13 NDIR measuring instrument

Claims (5)

A volatile organic compound measuring device that measures the amount of volatile organic compounds containing oxygenated hydrocarbons contained in the ambient air,
An air intake section for taking in the atmospheric air;
A concentration column for adsorbing and concentrating volatile organic compounds contained in the air taken in by the air take-in part;
A desorption promoting part that promotes desorption of the concentrated volatile organic compound from the concentration column;
A catalytic oxidation unit that oxidizes a volatile organic compound desorbed from the concentration column in the presence of an oxidation catalyst to generate carbon dioxide;
A volatile organic compound measuring device comprising: an output unit that measures the amount of carbon dioxide generated in the catalytic oxidation unit by a non-dispersive infrared absorption method and outputs a carbon-converted volatile organic compound amount.   The volatile organic compound measuring apparatus according to claim 1, wherein the desorption promoting unit heats the concentration column to promote desorption of the volatile organic compound from the concentration column.   The volatile property according to claim 2, wherein the desorption promoting unit includes a cooling unit that cools the concentration column after the volatile organic compound is desorbed from the concentration column by heating the concentration column. Organic compound measuring device. A zero gas generation unit that generates zero gas from which carbon dioxide and moisture have been removed from the atmosphere taken in by the air intake unit;
The volatile organic compound measuring apparatus according to claim 1, wherein the concentration column is washed by causing the zero gas generated by the zero gas generation unit to flow through the concentration column. A volatile organic compound measuring method for measuring the amount of volatile organic compounds containing oxygenated hydrocarbons contained in environmental air,
An air intake process for capturing environmental air;
A concentration step in which volatile organic compounds contained in the taken-in air are adsorbed on a concentration column and concentrated;
A desorption step of desorbing the concentrated volatile organic compound from the concentration column, wherein the desorption step promotes desorption;
A catalytic oxidation step in which desorbed volatile organic compounds are oxidized in the presence of an oxidation catalyst to generate carbon dioxide;
An output step of measuring the amount of generated carbon dioxide by a non-dispersive infrared absorption method and outputting the amount of a volatile organic compound in terms of carbon, and a method for measuring a volatile organic compound.

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