JP4874946B2 - Gas concentration cell and gas concentration method - Google Patents

Description

  The present invention relates to a concentration cell for collecting and concentrating a trace gas present in a gas, and a gas concentration method.

  Hazardous air pollutants such as benzene, toluene and xylene are considered to have high health risks. Sensitive measurements of these substances in the atmosphere and continuous measurements in the field are important issues. Conventionally, for such a measurement, a measuring apparatus that collects and measures a sample by using a micro flow cell has been proposed (see, for example, Patent Document 1 and Patent Document 2).

  FIG. 1 is a configuration diagram showing an outline of a conventional measuring apparatus using a micro flow cell. This measuring apparatus is roughly composed of a concentration cell 1 and a measuring cell 2. The concentration cell 1 heats and desorbs the gas flow path 11 for circulating the gas to be measured, the adsorbent 12 filled in the gas flow path 11, and the substance adsorbed and fixed to the adsorbent 12. A thin film heater 13 is provided. The adsorbent 12 includes, for example, a porous silica material. On the other hand, the measurement cell 2 is provided with an ultraviolet light path / gas flow path 21 that allows the gas to be measured from the gas flow path 11 to flow and allows the measurement ultraviolet light to pass therethrough.

  The measuring apparatus further connects a gas introduction flow path 14 for allowing the gas to be measured to flow into the gas flow path 11 of the concentration cell 1, the gas flow path 11 of the concentration cell 1, and the ultraviolet light path / gas flow path 21 of the measurement cell 2. A connecting flow path 3 that communicates and a gas discharge flow path 22 that discharges the gas that has been measured from the measurement cell 2 are provided.

  The measuring device includes a pump 4 that introduces gas from the atmosphere into the gas introduction flow path 14, a power supply 15 that heats the thin film heater 13, an ultraviolet light source 5 that generates ultraviolet light incident on the ultraviolet light path / gas flow path 21, and a collection of ultraviolet light. There are provided lenses 8 a and 8 b that emit light and an ultraviolet detector 6 that detects ultraviolet rays emitted from the ultraviolet light path / gas passage 21. The ultraviolet rays collected by the lens 8 b and dispersed by the grating 9 are detected by the ultraviolet detector 6. The detected signal is subjected to data processing or the like by the personal computer 7 or the like. The measurement result is output or displayed on the personal computer 7.

  In the measuring apparatus configured as described above, for example, air containing benzene is sucked by the pump 4 and flows into the concentration cell 1, and benzene is adsorbed and fixed to the adsorbent 12. After a certain time has elapsed, the thin film heater 13 is driven by the power source 15 and the adsorbent 12 is heated, whereby the benzene adsorbed and fixed on the adsorbent 12 is desorbed and separated. The desorbed and separated benzene is guided to the measurement cell 2 through the connection channel 3, and benzene is detected by absorption spectroscopy in the measurement cell 2.

Japanese Patent Laid-Open No. 2003-021595 JP 2004-261672 A

  FIG. 2 is a diagram illustrating the configuration of the concentration cell 1 in the prior art. FIG. 2A is a top view, a cross-sectional view, and a bottom view showing the structure of the concentration cell. FIG. 2B is a diagram for explaining the operation of the concentration cell. In the concentration cell 1, a gas flow path 11 including an introduction flow path 31 and a discharge flow path 32 is formed in a substrate such as glass. The gas flow path 11 includes flow path portions 11 a and 11 b for installing the adsorbent 12. In FIG. 2A, the adsorbent 12 is filled in the flow path portion 11a. A thin film heater 13 for heating the substance adsorbed and fixed to the adsorbent 12 is installed on the bottom surface of the concentration cell 1 immediately below the flow path portion 11a.

  Any shape as viewed from the top view of the flow path portions 11a and 11b of the gas flow path 11 may be used, but usually a wide triangular shape is adopted so that the adsorbent 12 can be easily filled. ing. The amount of gas collected by the concentration cell 1 is determined by the gas concentration in the atmosphere, the flow rate of the atmosphere passing through the adsorbent 12 and the volume of the adsorbent 12. After a predetermined amount of air has flowed into the concentration cell 1, the gas adsorbed on the adsorbent 12 is desorbed by heating the heater 13.

  FIG. 2B is a diagram showing a gas concentration time change in the concentration cell in a series of operations of the concentration cell 1. The gas concentration in the concentration cell 1 is adsorbed to the adsorbent 12 as the air flows in, and the amount of adsorption increases approximately linearly. Thereafter, as shown in FIG. 2B, the heater is turned on and heat desorption is performed, whereby the gas concentration rapidly decreases and becomes zero. In general, in a region where the gas concentration in the concentration cell, that is, the amount of adsorption to the adsorbent 12 increases linearly, the gas concentration depends on the volume of the adsorbent 12 and saturates at a constant value with time. Therefore, in order to further increase the concentration of gas concentrated in the concentration cell 1, it is preferable that a sufficient volume of the adsorbent 12 in the concentration cell 1 is secured and a sufficient collection time is passed. It was.

  However, according to the study by the inventors, even if the volume of the adsorbent in the concentration cell 1 is increased as in the above-described conditions, the time change of the gas concentration in the concentration cell 1 shows a different behavior and is expected. It was found that the gas concentration cannot be increased as much. This different behavior of the change in gas concentration over time has been an impediment to improving the gas concentration detection sensitivity in the measuring apparatus. Next, this inhibition factor will be described in more detail.

  FIG. 3 is a diagram showing the time change of the benzene concentration in the concentration cell 1 with the volume of the adsorbent as a parameter, taking the case of benzene as an example. Curve (a) shows the change in benzene concentration over time when the adsorbent volume is relatively large, and curve (b) shows the change in benzene concentration over time when the adsorbent volume is relatively small. As is clear from FIG. 3, in the case of the curve (a) with a large adsorbent volume, the temporal increase rate (curve slope) of the benzene concentration is small as compared with the curve (b) with a small adsorbent volume. . After about 1 hour, the benzene concentration tended to be saturated, and the saturation value of the benzene concentration was lower than in the case of the curve (b). On the other hand, in the case of the curve (b) in which the volume of the adsorbent is relatively small, the temporal increase rate of the benzene concentration is larger. Although saturation was reached in a short time of about ten minutes, the saturation value of the benzene concentration was higher than that in the case of curve (a).

  As described above, the reason why the collection efficiency is not improved when the volume of the adsorbent is (a) is considered to be due to a decrease in the flow rate of the atmospheric sample. Since the flow rate of the air sample is lowered by the adsorbent filled in the flow path, it takes a long time to collect benzene. This is because moisture other than benzene is adsorbed during the compensation time, and the adsorbent adsorption capacity is saturated.

  An object of the present invention is to solve the problem that the collection efficiency of the gas to be measured is not sufficiently improved even if the volume of the adsorbent is increased as described above. The collection efficiency by the prior art concentration cell is further improved, and the detection sensitivity of the gas concentration in the detection device is improved.

  In order to achieve the above object, the invention of the gas concentration cell according to claim 1 of the present invention includes a gas flow path through which the atmospheric sample flows in the gas concentration cell that collects the analysis target gas from the atmospheric sample. A first adsorbent provided in a part of the gas flow path for adsorbing or desorbing the analysis target gas; and at least one control means for desorbing the target gas from the first adsorbent. The pre-stage cell, wherein the pre-stage cell repeats the analysis target gas adsorption operation and the analysis target gas desorption operation alternately multiple times, and at each of the repeated desorption operations in the pre-stage cell, the pre-stage cell A gas flow path through which the analysis target gas desorbed in (2) flows, a second adsorbent provided in a part of the gas flow path for adsorbing or desorbing the analysis target gas, and the analysis pair from the second adsorbent. A second-stage cell including a second control means for desorbing gas, and after the target analysis gas is cumulatively adsorbed to the second adsorbent for each desorption operation of the former-stage cell, the second cell The gas to be analyzed is desorbed from the adsorbent and discharged to the outside of the rear cell, and the flow channel switching means connected between the front cell and the rear cell, And switching to one of a flow path for discharging the atmospheric sample flowing through the front stage cell to the outside of the gas concentration cell and a flow path for connecting the front stage cell to the rear stage cell. The flow rate is characterized by being larger than the gas flow rate of the flow path of the latter cell.

  Invention of Claim 2 is a gas concentration cell of Claim 1, Comprising: The volume of the said 1st adsorbent in the said front | former stage cell is a volume of the said 2nd adsorbent in the said back | latter stage cell. It is characterized by being smaller than.

  The invention according to claim 3 is the gas enrichment cell according to claim 1 or 2, wherein the at least one preceding cell is composed of a plurality of preceding cells arranged in parallel, and the plurality of preceding cells. The adsorption operation and the desorption operation are performed in synchronization with each other, and the gas to be analyzed from the plurality of preceding cells desorbed during the desorption operation is merged and flows into the subsequent cell.

  Invention of Claim 4 is the gas concentration cell in any one of Claim 1 thru | or 3, Comprising: In order to isolate | separate the said analysis object gas and other component gas from the said air | atmosphere sample, The flow path is switched by the flow path switching means using the difference in desorption temperature between the analysis target gas and the other component gases in the front stage cell, and only the analysis target gas is transferred to the rear stage cell. It is characterized by.

  According to a fifth aspect of the present invention, in the gas detection apparatus for collecting and analyzing the analysis target gas from the atmospheric sample, the analysis target gas provided in a part of the gas flow path through which the atmospheric sample flows and the gas flow path A first adsorbent that adsorbs or desorbs the first adsorbent and first control means for desorbing the target gas from the first adsorbent, wherein the analysis target gas adsorbing operation is performed. Alternately repeating the desorption operation of the analysis target gas a plurality of times, and a gas flow path through which the analysis target gas desorbed in the previous stage cell flows during each repeated desorption operation in the previous stage cell; and A second-stage cell that includes a second adsorbent that is provided in part and adsorbs or desorbs the analysis target gas; and a second control unit that desorbs the analysis target gas from the second adsorbent, in front After the target analysis gas is cumulatively adsorbed to the second adsorbent for each desorption operation of the cell, the analysis target gas is desorbed from the second adsorbent and discharged to the outside of the subsequent cell. And measuring the concentration of the analyte gas desorbed from the former cell for each desorption operation, or the analyte to be desorbed from the latter cell, between the former cell and the latter cell. A detection cell for measuring a gas concentration; and a first flow path switching unit disposed between the front cell and the detection cell, wherein the flow of the analysis target gas from the front cell to the detection cell Switching to one of the flow paths and the flow path for flowing the analysis target gas from the subsequent cell to the detection cell, and switching the second flow path disposed between the detection cell and the subsequent cell Any one of a flow path for flowing the analysis target gas from the previous stage cell flowing through the detection cell to the subsequent stage cell and a flow path for discharging the analysis target gas from the subsequent stage cell to the outside. And a third flow path switching means disposed on the discharge side of the subsequent cell, the flow for discharging the gas to be analyzed from the preceding cell via the first flow path switching means. A flow path for discharging the analysis target gas from the rear cell, a flow path for discharging the analysis target gas from the rear cell, and the first flow path for the analysis target gas desorbed from the rear cell. A gas detection apparatus comprising: switching to one of flow paths flowing to the detection cell via a switching unit.

  The invention according to claim 6 is the gas concentration cell or the gas detection device according to any one of claims 1 to 5, wherein the analysis target gas is any one of benzene, toluene and xylene. It is characterized by being.

  The invention according to claim 7 is constituted by at least one front cell having a high-speed gas flow path and a rear cell having a low-speed gas flow path, and is analyzed in a gas concentration cell that collects an analysis target gas from an air sample. In the method of concentrating the target gas, following the first step of adsorbing the analysis target gas to the first adsorbent disposed in the flow path in the preceding cell, and the first step of adsorbing, A second step of desorbing the analysis target gas collected by the first adsorbent and a second step of disposing the analysis target gas desorbed in the second step of desorption in a flow path in the rear cell. The third step of adsorbing to the second adsorbent and the first step to the third step are repeated a predetermined number of times, and the analysis target gas is accumulated in the second adsorbent cumulatively. An invention of a method for concentrating a gas, characterized in that it comprises a fourth step of.

  The invention according to claim 8 is a method for concentrating the gas according to claim 7, wherein the volume of the first adsorbent in the front cell is the second adsorbent in the rear cell. It is characterized by being smaller than the volume.

  According to the ninth aspect of the present invention, at least one front-stage cell having a high-speed gas flow path, a rear-stage cell having a low-speed gas flow path, a measurement target gas disposed between the front-stage cell and the rear-stage cell. A gas concentration device configured to collect a gas to be analyzed from an air sample, and a method for measuring the concentration of the gas to be analyzed in a gas concentration device configured to measure a concentration; A first step of adsorbing the gas to be analyzed to the adsorbent, and a second step of desorbing the gas to be analyzed collected by the first adsorbent following the first step of adsorbing. A third step of measuring the concentration of the analysis target gas while flowing the analysis target gas desorbed in the second step of desorption through the detection cell; and a flow through the detection cell. In addition, the fourth step of adsorbing the gas to be analyzed to the second adsorbent disposed in the flow path in the subsequent cell and the first step to the fourth step are repeated a predetermined number of times. Repeatedly, after the fifth step of concentrating the analysis target gas cumulatively in the second adsorbent and the fifth step of concentrating, the second adsorbent cumulatively concentrated in the second adsorbent. An invention of a method for measuring gas concentration, comprising: a sixth step of desorbing an analysis target gas; and a seventh step of measuring the concentration of the desorbed analysis target gas in the detection cell. is there.

  A tenth aspect of the invention is a method for measuring a gas concentration according to the ninth aspect, wherein the concentration of the analysis target gas measured in the third step of performing the concentration measurement is a predetermined value. If the measured value exceeds the value, the concentration measurement is terminated using the measured value as the final measured value.

  ADVANTAGE OF THE INVENTION According to this invention, the concentration cell collection efficiency can be improved conventionally and the detection sensitivity of to-be-measured gas concentration can be improved.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 4 is a diagram showing the configuration of the gas concentration cell according to the first embodiment of the present invention. The gas concentration cell of the present embodiment is configured by a high-speed flow cell 1a arranged at the front stage and a low-speed flow cell 1b arranged at the rear stage. The atmospheric sample is introduced into one end 31a of the preceding high-speed flow cell 1a through a pump (not shown). The other end 32a of the high-speed flow cell 1a is connected to the downstream low-speed flow cell 1b via the three-way valve 30.

  The three-way valve 30 has two outlet ports 33 and 34. The outlet port 33 of the three-way valve 30 is also connected to the outside. Therefore, the discharge path of the atmospheric sample in the high-speed flow cell 1a in the preceding stage is a path (POS.I) through which the atmospheric sample is discharged to the outside depending on the position setting state (POS.I or POS.II) of the three-way valve 30. And one of two paths (POS. II) for discharging to the downstream low-speed flow cell 1b.

  On the other hand, the outlet port 34 of the three-way valve 30 is connected to one end 31b of the subsequent low-speed flow cell 1b, and the other end 32b of the low-speed flow cell 1b is connected to a measurement cell not shown in the figure. The high-speed flow cell 1a includes gas flow path portions 11a and 11b for circulating the gas to be measured. Similarly, the low-speed flow cell 1b includes gas flow path portions 11c and 11d for circulating the gas to be measured. The high-speed flow cell 1a and the low-speed flow cell 1b include adsorbents 12a and 12b filled in the gas flow path portions 11a and 11c, respectively, and a thin film heater that heats the substance adsorbed and fixed to the adsorbent. With structure. The high-speed flow cell 1a secures the flow rate of the atmospheric sample by reducing the volume of the adsorbent 12a filled in the gas flow path portion 11a, and enables high-speed inflow of the atmospheric sample. The adsorbent 12 includes, for example, a porous silica material.

  In the gas concentration cell of the present invention, hereinafter, the high-speed flow cell 1a disposed on the front stage side of the entire flow path is referred to as a front stage cell. On the other hand, the low-speed flow cell 1b arranged on the rear stage side of the entire flow path is called a rear stage cell.

  In the gas concentration cell of the present invention, the front cell 1a repeatedly adsorbs and desorbs the target gas at regular time intervals and transfers it toward the rear cell 1b. The post-stage cell 1b operates so as to exhaust the target gas transferred from the pre-stage cell 1a to the measurement cell by cumulatively adsorbing and then desorbing the target gas.

  FIG. 5 is a diagram for explaining the operation of the gas concentration cell of the present embodiment. A case where the concentration of benzene in the atmosphere is measured will be described as an example. FIG. 5 shows (A) the setting position of the three-way valve, (B) the benzene concentration of the front cell, (C) the temperature of the front cell, (D) the benzene concentration of the rear cell, and (E) the temperature of the rear cell. The time transition is shown synchronously. First, in period (1), the three-way valve 30 is POS. The state I is set and the atmospheric sample is taken into the front cell 1a by the pump. At this time, a path for discharging to the outside from the three-way valve 30 is formed, and the benzene gas in the atmospheric sample is adsorbed by the adsorbent 12a with the passage of time, and its concentration increases.

  Next, in the period (2), the three-way valve 30 is POS. The path is set to the state II and connects the front cell 1a with the rear cell 1b. At the same time, the heater of the front cell 1a is turned on to raise the temperature in the front cell 1a. When the in-cell temperature is equal to or higher than the desorption temperature of benzene gas, the benzene gas is desorbed from the adsorbent and transferred to the subsequent cell 1b. The transferred benzene gas is adsorbed by the adsorbent 12b in the rear cell 1b. In this state (2), desorption is completed in the front cell 1a, the benzene concentration becomes almost zero, and the adsorbent returns to the initial fresh state. On the other hand, in the state (2), the benzene concentration increases in the rear cell 12b.

  The operation of the gas concentration cell of this embodiment further shifts to the period (3), and the three-way valve 30 is again POS. The position is set to I and the heater of the front cell 1a is turned off. Thereafter, in the period (3) to the period (8), the same operation as the cycle 1 including the period (1) to the period (2) is repeated as the cycle 2, the cycle 3, and the cycle 4. It should be noted that in the front cell 1a, the adsorption and desorption of benzene gas are repeated, and the adsorbent returns to the initial fresh state every cycle. In the rear cell 1b, benzene gas is adsorbed cumulatively. After a predetermined cycle is repeated, in the period (9), the three-way valve 30 is set to POS. When the state II is set and the heater of the rear cell 1b is turned on, the benzene gas to be analyzed that is accumulated and adsorbed in the rear cell 1b is desorbed and discharged toward the measurement cell.

  The effect of the gas concentration cell of this embodiment was confirmed by replacing the concentration cell 1 of the prior art shown in FIG. 1 with the two-stage concentration cells 1a and 1b of this embodiment. The sample air containing benzene was concentrated by the procedure described in FIG. 5, and after repeating a certain number of concentration cycles, it was introduced into a measurement cell and subjected to absorption analysis. Details will be described below.

  FIG. 6 is a diagram showing the relationship between the concentration time and the absorbance by the gas concentration cell of the first embodiment. The vertical axis in FIG. 6 shows the absorbance measured at a wavelength of 253 nm, which is the absorption peak of benzene, with respect to the concentrated gas introduced into the measurement cell. The horizontal axis indicates the concentration time (minutes) executed until introduction into the measurement cell. The plot group (A) uses the gas enrichment cell having the two-stage configuration according to the first embodiment of the present invention, and the plot group (B) uses the gas enrichment cell having the one-stage configuration of the prior art. Respectively. In addition, the volume of the adsorbent of the gas concentration cell of the two-stage configuration of the present invention is small in the front cell and large in the rear cell. The conventional one-stage gas concentration cell for comparison is the same as the previous-stage concentration cell in the above-described two-stage gas concentration cell, and the volume of the adsorbent is approximately equal to that of the previous-stage concentration cell.

  As is apparent from FIG. 6, in the case of the plot group (A) using the gas concentration cell of the present invention, the absorbance increases almost linearly as the concentration time increases. That is, it can be seen that as the concentration time elapses, the gas concentration continuously proceeds in the gas concentration cell of the present invention.

  On the other hand, in the case of the plot group (B), the absorbance is saturated after the first concentration time of about 10 minutes. Moreover, the saturated absorbance value was smaller than in the plot group (A). That is, in the case of the gas concentration cell of the prior art, the absorbance reaches the saturation state in a short time of about 10 minutes, and the gas concentration does not progress any more than that.

  In the case of the plot group (B), even when the volume of the adsorbent was increased, the time to reach the saturation of absorbance did not increase, but rather the saturation level decreased. Therefore, the gas concentration performance cannot be improved by increasing or decreasing the adsorbent of the conventional one-stage concentration cell. By using the two-stage concentration cell of the present invention, the concentration of benzene can be continuously increased linearly without saturation, and the efficiency of concentration collection can be improved. It was confirmed that the detection sensitivity of the gas concentration in the detection cell can be greatly improved by using the two-stage concentration cell of the present invention.

  The gas flow rate in the front cell of the present invention is approximately 100 sccm, and the gas flow rate in the rear cell is approximately 20 sccm. The volume (volume) of the adsorbent in the front cell is 0.5 to 3 μl, and the capacity of the adsorbent in the rear cell is 6 to 10 μl.

(Second Embodiment)
By further contriving the operation of the three-way valve using the gas concentration cell according to the configuration of the above-described embodiment, one type of gas is selected and concentrated from a mixed gas containing a plurality of contaminants having different heat desorption temperatures. You can also. Hereinafter, the second embodiment will be described in detail.

  FIG. 7 is a diagram for explaining the principle of separating and concentrating only one gas from the mixed gas. More specifically, a case where only benzene is separated and concentrated from a mixed gas composed of benzene, toluene and xylene (hereinafter, this mixed gas is abbreviated as BTX) will be described as an example. 7A shows a state diagram of the flow path switched by the three-way valve, and FIG. 7B shows a temperature rise profile in the preceding cell. Referring to the part (B), it means that benzene, toluene and xylene are desorbed in this order as the temperature rises. The desorption temperatures of benzene, toluene, and xylene are about 100 degrees, about 160 degrees, and about 180 degrees, respectively, when using a certain type of adsorbent. In the following description, reference is also made to FIG.

  In the present embodiment, first, in the period (1), the three-way valve 30 is set to POS. The state is set to I, and the mixed gas containing BTX is taken into the front cell 1a by a pump. The three-way valve 30 is formed with a path for discharging to the outside via the outlet port 33. As time elapses, BTX in the air sample is adsorbed by the adsorbent 12a in the pre-stage cell 1a and its concentration increases. The operation so far is similar to the period (1) shown in FIG.

  Next, in period (2) -1, the three-way valve 30 is set to POS. The state is set to II, and a path connecting the front cell 1a and the rear cell 1b is formed. At the same time, the heater of the front cell 1a is turned on to raise the temperature in the front cell 1a. When the temperature in the front cell 1a exceeds the desorption temperature TempB of benzene, benzene is first desorbed from the adsorbent and transferred to the rear cell 1b. The desorption of benzene is completed in a short time on the order of minutes after the desorption temperature TempB is exceeded.

  Further, the temperature is continuously increased by the heater, and at the start point of the period (2) -2 where the toluene desorption temperature TempT is reached, the three-way valve 30 is set to POS. Set to state I. At this time, desorption of toluene and xylene starts in this order, and toluene and xylene are discharged to the outside through the outlet port 33. Therefore, only the benzene of the BYX mixed gas is separated from the front cell 1a and transferred to the rear cell 1b. In period (2) -2, after toluene and xylene are discharged, the adsorbent 12a in the front cell 1a returns to the initial fresh state.

  As shown in FIG. 7, by repeating one cycle from the period (1) to the period (2) -2 in which only benzene is transferred to the subsequent cell 1b, benzene is repeatedly accumulated in the subsequent cell 1b. After repeatedly performing a certain number of cycles, when the heater of the rear cell 1b is turned on, the accumulated benzene in the rear cell 1b is desorbed and discharged toward the measurement cell. Therefore, the period (2) in FIG. 5 describing the first embodiment may be replaced with the period (2) -1 and the period (2) -2 in FIG. In addition, the temperature rise profiles in the period (2) -1 and the period (2) -2 should be gradual and linear so that the desorption of toluene can be started after the desorption of benzene is reliably completed. Is preferred.

  When separating the above-mentioned benzene, it is also possible to separate only toluene from BTX. In this case, first, the three-way valve 30 is set to POS. Set to state I, benzene is desorbed and discharged to the outside. Next, the three-way valve 30 is connected to the POS. In the state I, toluene is desorbed and transferred to the rear cell 1b. Finally, the three-way valve 30 is again set to POS. What is necessary is just to set to the state of I, to desorb xylene, and to discharge | emit outside. Similarly, to separate only xylene, the three-way valve 30 is connected to the POS. In the state I, benzene and toluene are desorbed in this order and discharged to the outside. When the desorption of toluene is completed, the three-way valve 30 is set to POS. If the setting is switched to the state I, only toluene can be transferred to the subsequent cell 1b.

(Third embodiment)
In the gas concentration cell having a two-stage configuration of the present invention, the preceding cell can also function as a water molecule filter. Moisture has a strong affinity for adsorbents such as mesoporous silica and carbon pack X, and adversely affects the separation and concentration of the target gas. In general, moisture has a higher heat desorption temperature than harmful volatile substances such as benzene, toluene and xylene. Therefore, moisture can be discharged to the outside by the same method as in the second embodiment, and only the target gas can be stored in the subsequent cell. That is, in the gas concentration cell having a two-stage configuration of the present invention, when the former cell functions as a water molecule filter, the former cell is raised so as to reach a temperature at which water molecules are desorbed.

  As shown in the second embodiment, in the temperature raising process, one or more of benzene, toluene, and xylene are thermally desorbed and transferred to the subsequent cell. Thereafter, the temperature is further raised and discharged when the water molecules are desorbed. By this operation, one or more of benzene, toluene, and xylene can be collected in the subsequent cell in a state where moisture is excluded.

(Fourth embodiment)
This embodiment is characterized in that a plurality of preceding cells are arranged in parallel in order to further increase the collection efficiency of the target gas.

  FIG. 8 is a diagram showing a configuration of a gas concentration cell in which two front-stage cells are arranged in parallel. In the present embodiment, the first front-stage cell 41a and the second front-stage cell 41b are arranged in parallel and connected to the first three-way valve 42a and the second three-way valve 42b, respectively. One outlet port of each of the two three-way valves is made into one common flow path by the junction pipe 43, and is connected to the inlet of the rear cell 41c. The other outlet ports of the two three-way valves 42a and 42b are connected to the outside. The discharge paths of the first front-stage cell 41a and the second front-stage cell 41b are discharged to the outside (POS.I) or the rear-stage cell 41c depending on the setting of the state of the three-way valves 42a and 42b, respectively. One of the paths (POS. II) is set. The above-described channel switching is the same as in the first embodiment.

  FIG. 9 is a diagram for explaining the operation of the gas concentration cell of the present embodiment. Also in this embodiment, the case where the benzene concentration in the atmosphere is measured will be described as an example. The first front cell 41a and the second front cell 41b transfer the target gas collected by the respective cells to the rear cell 41c at different timings. Hereinafter, the transfer operation at different timings will be described. In FIG. 9, (A) the three-way valve setting position, (B) the benzene concentration and (C) the cell temperature for the first front cell, (D) the three-way valve for the second front cell. The valve setting position, (E) benzene concentration and (F) cell temperature, and (G) benzene concentration and (H) cell temperature are synchronized with the subsequent cells, with each temporal transition synchronized. Indicated.

  First, in the period (1), the first three-way valve 42a is POS. In the state I, benzene gas in the atmospheric sample is collected in the first front cell 41a. After a predetermined time td, the second three-way valve 42b is moved to POS. In the state I, benzene gas in the atmospheric sample is collected in the second front cell 41b.

  Next, when the period (2) is started, the first three-way valve 42a is set to POS. At the same time, the heater of the first front cell 41a is turned on, and the cell internal temperature of the first front cell is raised. When the internal temperature of the cell becomes equal to or higher than the desorption temperature of the benzene gas, the benzene gas is desorbed from the adsorbent and transferred to the subsequent cell 41c. The transferred benzene gas is adsorbed by the adsorbent in the rear cell 41c.

  In the period (2), the second front cell 41b is still collecting benzene gas, but in the period (3) after the end of the period (2), the heater of the second front cell 41b is turned off. When ON, the cell internal temperature of the second previous stage cell 41b is raised. When the internal temperature of the cell becomes equal to or higher than the desorption temperature of the benzene gas, the benzene gas is desorbed from the adsorbent and transferred to the subsequent cell 41c. The transferred benzene gas is adsorbed by the adsorbent in the rear cell 41c. As described above, the first front-stage cell 41a and the second front-stage cell 41b independently collect benzene gas and transfer it to the rear-stage cell 41c at different times. The two preceding cells alternately repeat the above collection and transfer cycle while operating in parallel.

  According to the gas concentrating operation by the gas concentrating cell in which the two preceding cells are arranged in parallel, the time required for the concentration of the target gas in the succeeding cell 41c to reach the target value is one when the preceding cell is one. Compared to ½. Here, the number of front-stage cells arranged in parallel is not limited to two, and can be a plurality of three or more within a possible range. Furthermore, by arranging n preceding cells in parallel, the measurement time required to obtain the same detection sensitivity for the gas concentration in the detection cell is approximately 1 / n compared to the case where there is one preceding cell. can do. Further, when the gas concentration time is the same, the detection sensitivity of the gas concentration can be increased by a factor of n compared to the case where there is only one preceding cell.

(Fifth embodiment)
The gas concentration cell of each embodiment described so far has a configuration suitable for concentrating gas to a high concentration in order to increase detection sensitivity in the measurement cell. For gas concentration, it is necessary that the front cell and the rear cell work together to repeat a certain concentration cycle. However, the gas concentration that needs to be measured varies depending on the measurement target gas and the target measurement environment. When the gas concentration cell of each of the above-described embodiments is used, for example, even when the measurement target gas has a sufficiently high concentration, the concentration cycle is repeated, so that the measurement efficiency is poor. According to the concentration cell of the present embodiment, the target gas can be measured even in the intermediate stage of the gas concentration cycle, and the measurement efficiency can be further improved.

  FIG. 10 is a diagram for explaining the configuration and operation of a gas concentration cell according to the fifth embodiment of the present invention. FIG. 10A shows the configuration of the gas concentration cell. In the gas concentration cell of this embodiment, a detection cell 67 is inserted through a first three-way valve 61 and a second three-way valve 62 in the transfer path from the front cell 66a to the rear cell 66b. Further, the outlet of the rear cell 66 b is connected to the introduction side of the detection cell 67 through the third three-way valve 63. Next, operation | movement of the gas concentration cell of this embodiment is demonstrated. FIG. 10B, FIG. 10C, and FIG. 10D are diagrams showing the respective flow path states I, II, and III that are switched in this order as time passes.

  In the flow path state I shown in FIG. 10B, the flow path L <b> 2 is connected to the outlet 1 by the first three-way valve 61 and the third three-way valve 63. In the case of this flow path state I, a path is formed in which an air sample is taken into the front cell 66a from the inlet by the pump 65 and discharged from the outlet 1 to the outside. As time passes, the target gas in the atmospheric sample is adsorbed by the adsorbent of the front cell 66a. In the flow path state I, the detection cell 67 is not operating, and the state position of the second three-way valve 62 is arbitrary.

  Subsequently, in the flow path state II shown in FIG. 10C, the states of the first three-way valve 61 and the second three-way valve 62 are switched. Note that a path in which the detection cell 67 is inserted is formed between the front-stage cell 66a and the rear-stage cell 66b via the flow path L1 and the flow path L4. The third three-way valve 63 is connected to the outlet 1.

  When the flow state shifts to II, the heater of the front cell 66a is turned on to increase the temperature in the front cell. When the temperature in the cell becomes equal to or higher than the desorption temperature of the target gas, the target gas is desorbed from the adsorbent of the front cell 66 a and transferred to the rear cell 66 b through the detection cell 67. The transferred target gas is adsorbed by the adsorbent in the rear cell 66b. At this time, the detection cell 67 is operated to measure the concentration of the gas passing through the detection cell 67.

  One cycle of the above-mentioned flow path state I and flow path state II is repeated several times. Here, it should be noted that the gas concentration is measured each time the target gas passes through the detection cell 67 while the transfer to the subsequent cell 66b is repeated. If the concentration of the target gas passing through the detection cell 67 satisfies the predetermined condition in the above-described one cycle (channel state I + channel state II), the measurement environment concentration can be grasped at that time. Can be terminated. For example, if a gas with a concentration higher than the allowable value is detected, the measurement is terminated because the concentration in the measurement environment can be grasped.

  When the gas concentration measured for each cycle by the detection cell 67 is low, the cycle (channel state I + channel state II) is repeated a predetermined number of times, and then the channel state III shown in FIG. 10D is reached. Transition. In the flow path state III, the states of the first three-way valve 61, the second three-way valve 62, and the third three-way valve 63 are switched. A path through which the rear cell 66b is connected to the detection cell 67 is formed via the flow path L3 and the flow path L2. The second three-way valve 62 is connected to the outlet 2.

  When the flow state III is entered, the heater of the rear cell 66b is turned on, and the internal temperature of the rear cell 66b is raised. The target gas to be analyzed accumulated in the subsequent cell 66 b is desorbed and transferred to the measurement cell 67 during a plurality of cycle periods repeated so far. The concentration of the transferred target gas is measured in the measurement cell 67.

  It should be understood that the present embodiment is characterized in that the gas concentration is measured in the detection cell 67 each time the target gas is transferred from the front cell 66a to the rear cell 66b. Recall that in each of the previously described embodiments, the gas concentration measurement was performed after a predetermined number of transfer cycles had been performed and the concentration to the subsequent cell was completed.

  As described above, in the gas concentration cell according to the configuration of the present embodiment, the concentration of the target gas is sequentially measured in the detection cell even in the intermediate stage of the gas concentration cycle. Measurement results can be determined even before the target gas is desorbed from the subsequent cell. Whether the target sample is a low concentration or a high concentration, it can be measured by one gas concentration cell configuration only by changing the state of each three-way valve. The dynamic range of the gas detection concentration of the entire measuring apparatus can be widened. Furthermore, since one common detection cell can be used, the cost of the measuring apparatus can be suppressed. It has the advantage that the gas concentration measuring device can be miniaturized.

  INDUSTRIAL APPLICABILITY The present invention can be used for a measuring device that performs high-sensitivity measurement of harmful substances in the atmosphere and continuous measurement in the field.

It is a block diagram which shows the outline | summary of the measuring apparatus using the trace flow cell of a prior art. (A) is a block diagram of the concentration cell of a prior art, (B) is a figure which shows the gas concentration time change in a concentration cell in a series of operation | movement. It is the figure which showed the time change of the benzene density | concentration of a concentration cell by using the volume of adsorption agent as a parameter. It is a figure which shows the structure of the gas concentration cell which concerns on the 1st Embodiment of this invention. It is a figure explaining operation | movement of the gas concentration cell which concerns on the 1st Embodiment of this invention. It is a figure which shows the relationship between the concentration time by the gas concentration cell of this invention, and a light absorbency. It is a figure explaining the principle which isolate | separates and concentrates only one gas from mixed gas. It is a figure which shows the structure of the gas concentration cell which arranged two front | former stage cells in parallel. It is a figure explaining operation | movement of the gas concentration cell which concerns on the 4th Embodiment of this invention. (A) is a figure which shows the structure of the concentration cell which concerns on 5th Embodiment, (B) is a figure which shows the flow-path state I, (C) is a figure which shows the flow-path state II, (D) is a flow-path state It is a figure which shows III.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concentration cell 1a, 41a, 41b, 66a Previous stage cell 1b, 41c, 66b Rear stage cell 2 Measurement cell 4, 65 Pump 5 Ultraviolet light source 6 Ultraviolet detector 11 Gas flow path 11a, 11b, 11c, 11d Flow path part 12, 12a , 12b Adsorbent 13 Heater 21 UV light path / gas flow path 30, 42a, 42b, 61, 62, 63 Three-way valve 67 Detection cell

Claims (10)

In the gas concentration cell that collects the gas to be analyzed from the air sample,
A gas flow path through which the atmospheric sample flows; a first adsorbent provided in a part of the gas flow path for adsorbing or desorbing the analysis target gas; and a first adsorbent for desorbing the target gas from the first adsorbent. At least one preceding cell including one control means, wherein the preceding cell alternately repeats the analysis gas adsorption operation and the analysis gas desorption operation a plurality of times;
In each of the repeated desorption operations in the preceding cell, a gas flow path through which the analysis target gas desorbed in the previous cell flows, and a second gas channel that is provided in a part of the gas flow path and adsorbs or desorbs the analysis target gas. And a second control means for desorbing the analysis target gas from the second adsorbent, the target analysis gas being added to the first cell for each desorption operation of the front cell. The cumulative adsorption to the second adsorbent, then desorbing the gas to be analyzed from the second adsorbent and exhausting it to the outside of the subsequent cell;
Channel switching means connected between the preceding cell and the succeeding cell, the channel switching means comprising: a channel for discharging the atmospheric sample flowing through the preceding cell to the outside of the gas concentration cell; and the preceding cell. Switching to one of the flow paths connected to the latter cell,
The gas concentration cell, wherein a gas flow rate of the flow path of the preceding cell is larger than a gas flow rate of the flow path of the subsequent cell.   The gas concentration cell according to claim 1, wherein the volume of the first adsorbent in the front cell is smaller than the volume of the second adsorbent in the rear cell.   The at least one front cell is composed of a plurality of front cells arranged in parallel, and the adsorption operation and the desorption operation in each of the plurality of front cells are performed in synchronization, and are desorbed during the desorption operation. 3. The gas concentration cell according to claim 1, wherein the analysis target gases from a plurality of preceding cells are merged and flow into the succeeding cell.   In order to separate the analysis target gas and the other component gases from the atmospheric sample, the flow path switching is performed using the difference in the desorption temperature between the analysis target gas and the other component gases in the preceding cell. The gas concentration cell according to any one of claims 1 to 3, wherein the flow path is switched by means to transfer only the analysis target gas to the subsequent cell. In the gas detector that collects and analyzes the target gas from the air sample,
A gas flow path through which the atmospheric sample flows; a first adsorbent provided in a part of the gas flow path for adsorbing or desorbing the analysis target gas; and a first adsorbent for desorbing the target gas from the first adsorbent. And at least one front-stage cell including one control means, wherein the adsorption operation of the analysis target gas and the desorption operation of the analysis target gas are alternately repeated a plurality of times;
During each repeated desorption operation in the preceding cell, a gas flow path through which the analysis target gas desorbed in the previous cell flows, and a second gas channel provided in a part of the gas flow path to adsorb or desorb the analysis target gas And a second control means for desorbing the analysis target gas from the second adsorbent, the target analysis gas being added to the first cell for each desorption operation of the front cell. After the cumulative adsorption to the second adsorbent, the analysis target gas is desorbed from the second adsorbent and discharged to the outside of the rear cell;
Concentration measurement of the analysis target gas, which is arranged between the front cell and the rear cell and is desorbed from the front cell for each desorption operation, or the concentration measurement of the analysis gas desorbed from the rear cell A detection cell that performs
A first flow path switching unit disposed between the front cell and the detection cell, the flow path for flowing the analysis target gas from the front cell to the detection cell, and the analysis target from the rear cell. Switching to one of the flow paths for flowing gas to the detection cell;
A second flow path switching unit disposed between the detection cell and the subsequent cell, the flow path for flowing the analysis target gas from the previous cell flowing through the detection cell to the subsequent cell; Switching to any one of the flow paths for discharging the gas to be analyzed from the subsequent cell to the outside;
A third flow path switching unit disposed on the discharge side of the rear cell, the flow path for discharging the analysis target gas from the front cell through the first flow path switching unit; A flow path for discharging the analysis target gas from the cell, a flow path for discharging the analysis target gas from the subsequent cell, and the analysis target gas desorbed from the subsequent cell via the first flow path switching means A gas detection device comprising: switching to one of flow paths flowing to the detection cell.   The gas concentration cell or gas detection device according to any one of claims 1 to 5, wherein the analysis target gas is any one of benzene, toluene, and xylene. In a method of concentrating an analysis target gas in a gas concentration cell configured to collect an analysis target gas from an air sample, which is composed of at least one front stage cell having a high speed gas flow path and a rear stage cell having a low speed gas flow path,
A first step of adsorbing the analysis target gas to a first adsorbent disposed in a flow path in the front cell;
Following the first step of adsorbing, a second step of desorbing the analysis target gas collected by the first adsorbent;
A third step of adsorbing the analysis target gas desorbed in the desorbing second step to a second adsorbent disposed in a flow path in the subsequent cell;
The first step to the third step are repeated a predetermined number of times, and a fourth step of concentrating the analysis target gas cumulatively in the second adsorbent is provided. A method of concentrating gas.   The method for concentrating a gas according to claim 7, wherein a volume of the first adsorbent in the front cell is smaller than a volume of the second adsorbent in the rear cell. Consists of at least one front-stage cell having a high-speed gas flow path, a rear-stage cell having a low-speed gas flow path, and a detection cell that is disposed between the front-stage cell and the rear-stage cell and measures the concentration of the measurement target gas In a gas concentrator that collects an analysis target gas from an air sample, in a method for measuring the concentration of the analysis target gas,
A first step of adsorbing the analysis target gas to a first adsorbent disposed in a flow path in the front cell;
Following the first step of adsorbing, a second step of desorbing the analysis target gas collected by the first adsorbent;
A third step of measuring the concentration of the analysis target gas while flowing the analysis target gas desorbed in the second step of desorption;
A fourth step of adsorbing the gas to be analyzed that has flowed through the detection cell to a second adsorbent disposed in a flow path in the subsequent cell;
A fifth step in which the first step to the fourth step are repeated a predetermined number of times, and the analysis target gas is cumulatively concentrated in the second adsorbent;
After the fifth step of concentrating, a sixth step of desorbing the analysis target gas cumulatively concentrated in the second adsorbent;
And a seventh step of measuring the concentration of the desorbed analysis target gas in the detection cell.   When the concentration of the analysis target gas measured in the third step of performing the concentration measurement exceeds a predetermined value, the concentration measurement is ended with the measured value as a final measured value. A method for measuring the concentration of the gas according to claim 9.

Images