JP3216838B2 - Gas sampling method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the sampling of gas components in air or exhaust gas, and more particularly to a method and an apparatus for sampling gas components contained in vehicle exhaust gas.

[0002]

2. Description of the Related Art Various methods have been proposed for sampling gas components in the atmosphere or exhaust gas, particularly gas components contained in vehicle exhaust gas.
As described in Japanese Patent No. 24849 or the like, there is a method using a constant volume sampling device (CVS device). The method using the CVS apparatus (CVS method) is a method in which exhaust gas is diluted with air to have a constant temperature and a constant flow rate, and a part of the gas is sampled. By analyzing the gas sampled in this manner, CO, H in the exhaust gas is analyzed.
The concentration of C, NOx, etc. can be measured.

In the CVS method, a critical flow venturi (CFV) is mainly used because the apparatus is simple and the gas amount can be easily measured. FIG. 6 shows a CVS using a conventional CFV.
A schematic diagram of the device is shown. This CVS device is a vehicle 100
An extension pipe 102 is connected to the exhaust tail pipe 101, and a duct 103 is connected to an end of the extension pipe 102. The duct 103 is further connected to a gas passage 105 leading to a blower 104. On the side of the gas passage 105 near the duct 103, a dilution air inlet 106 and a mixing unit 107 for mixing the introduced air and exhaust gas are provided. Further, a critical flow venturi 1 for stabilizing the gas flow velocity is provided on the suction side of the blower 104.
08 is provided.

The gas flow rate (Qs) at the inlet of the critical flow venturi 108 can be expressed by the following equation (1). In the equation, C is the Venturi coefficient, Pin is the Venturi inlet pressure, and Tin is the Venturi inlet temperature.

[0005]

(Equation 1)

Since the gas flow rate is stable near the inlet of the critical flow venturi 108, the sampling venturi 10
9 is installed. And this sampling venturi 1
From 09, a fixed amount of the diluted exhaust gas is sampled using the sample pump 110. The gas sampled in this manner is supplied to an impinger assembly 111 serving as a gas collection unit.
Absorbing liquid 11 in a plurality of impinger 112 prepared inside
Absorb to 3 The impinger 112 is the ice bath 11
4 keeps the temperature constant. Further, a gas dryer 115 is arranged on the gas suction port side of the sample pump 110. Further, on the gas discharge side, a gas flow control valve 116,
A flow meter 117, a gas temperature measuring device 118, and a dry gas meter 119 are connected, whereby the gas flow rate can be adjusted, and the total amount of gas passing through the impinger 112 after temperature correction can be known.

[0007]

In the above-described method using the CVS apparatus, the temperature of the sampling gas is measured as described above. However, the pressure, which is another important factor, is merely regarded as a pseudo atmosphere. The actual pressure was not measured. Therefore, pressure correction could not be performed.
Further, since the pressure measurement is not performed in this manner, it is difficult to adjust the pressure of the gas flowing in the gas passage 105 to a pressure suitable for sampling, and further, the pressure before and after the impinger is reversed, resulting in a measurement failure. Trouble had occurred.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention introduces a target gas to a gas sampling device, absorbs the gas in a gas collecting portion provided in the gas sampling device, The gas flow rate is measured by a flow meter provided downstream of the flow meter, the gas flow rate is controlled by a flow rate control valve provided downstream of the flow meter, and a gas pump is further provided by a sample pump provided downstream of the flow rate control valve. The present invention relates to a gas sampling device for sucking a gas, wherein a sampling passage is opened on the gas inlet side of the gas collecting unit when on, the sampling passage on the inlet side is closed when off, and the sampling passage on the outlet side is open to the atmosphere. A first three-way valve is provided, and a sampling passage is opened between the gas collection unit and the flow meter when the gas is on, and a sump on the outlet side is turned off when the gas is collected. A second three-way valve that closes the sampling passage and opens the sampling passage on the inlet side to the atmosphere, and further adjusts the pressure in the sampling passage by sucking outside air between the flow control valve and the sample pump. A branch pipe with a pressure control valve is provided.

In the above gas sampling device,
A first pressure gauge on a gas inlet side of the first three-way valve;
It is also possible to add a second pressure gauge to the gas outlet side of the second three-way valve.

[0010]

According to the gas sampling method of the present invention, the target gas is guided to the gas sampling device, the gas is absorbed by the gas collecting portion provided in the gas sampling device, and the flow is provided on the downstream side of the gas collecting portion. The gas flow rate is measured by a meter, the gas flow rate is controlled by a flow rate control valve provided downstream of the flow meter, and the gas is sucked by a sample pump provided downstream of the flow rate control valve. On the gas inlet side of the gas collecting unit, a first three-way valve is provided that opens the sampling passage when on, closes the sampling passage on the inlet side when off and opens the sampling passage on the outlet side to the atmosphere when off, Between the gas collecting unit and the flow meter, a sampling passage is opened when on, a sampling passage on the outlet side is closed when off, and a sampling passage on the inlet side. A second three-way valve that opens to the atmosphere is installed, and a branch pipe provided with a pressure control valve that adjusts the pressure of the sampling passage by sucking outside air is provided between the flow rate control valve and the sample pump. First, the first and second three-way valves are turned off, and after the sample pump is operated, the second three-way valve is turned on. After a predetermined time, the first three-way valve is turned on to start gas sampling. This makes it possible to control the gas pressure in the sampling passage.

The predetermined time in the gas sampling method is a time required for the gas outlet side pressure of the second three-way valve to drop by a predetermined pressure from the inlet side pressure of the first three-way valve.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, a gas sampling device and a sampling method suitable for sampling carbonyls such as formaldehyde, acetaldehyde, and acetone, which are non-methane HCs, and alcohols such as methanol and ethanol will be described. These non-methane HCs
It is a compound that greatly contributes to the generation of ozone that forms the ozone layer, which has recently been taken up as one of the most important issues in the atmospheric environment. In addition, the applicable range of the gas sampling device and the sampling method according to the present invention is not limited to the non-methane-based HC, and other substances can be obtained simply by changing the absorption liquid in the impinger, which is a gas collection unit. It can be applied to sampling of

FIG. 1 shows a schematic diagram of a gas sampling device according to the invention. In this figure, the parts other than those surrounded by broken lines are the same as those of the conventional apparatus described above. That is, an extension pipe 3 is connected to the exhaust tail pipe 2 of the vehicle 1, a duct 4 is connected to an end of the extension pipe 3, and the duct 4 is further connected to a gas passage 6 leading to a blower 5. Further, a dilution air inlet 7 and a mixing unit 8 for mixing the introduced air and exhaust gas are provided on the gas passage 6 near the duct 4. Further, a critical flow venturi 9 for stabilizing the gas flow velocity is provided on the suction side of the blower 5.

A sampling gas inlet 10 is provided near the inlet of the critical flow venturi 9, and a certain amount of the diluted exhaust gas is sampled by a sample pump 12 from the sampling gas inlet 10 through a sampling passage 11.

FIG. 2 is an enlarged view of a portion surrounded by the broken line. In order from the most upstream part of the sampling passage 11, the first
The pressure gauge 13, the first three-way valve 14, the impinger assembly 15, and the second three-way valve 16 are connected. Among them, the impinger assembly 15 which is a gas collecting unit will be described later. The first three-way valve 14 and the second three-way valve 16 are on-off type, and both ends of the impinger assembly 15 can be open to the atmosphere when off.

A flow meter 18 and a gas flow control valve 19 are further provided downstream of the second three-way valve 16 with a gas dryer 17 interposed therebetween. The flow meter 18 is for checking whether or not the gas flow rate flowing in the sampling passage 11 is normal. The gas flow rate can be adjusted by a gas flow rate control valve 19. On the gas outlet side of the gas flow control valve 19, a second pressure gauge 20 and a dry gas meter 21 for measuring the total gas passing amount are further mounted in this order, and a sample pump 12 is connected to the end. Further, a gas temperature measuring device 22 for detecting temperature is connected to the dry gas meter 21. on the other hand,
In the sampling passage 11 between the dry gas meter 21 and the sample pump 12, a branch pipe 23 for adjusting the pressure of the sampling passage 11 by sucking outside air is provided. A filter 25 is provided.

The arrangement of the sample pump 12 is different from that of the conventional example. However, there is no particular difference in the performance due to the difference in the installation location, and in the present invention, the sample pump 12 may be disposed at either side. This sample pump 12
Denotes a suction pump, which sucks the sample gas from the sampling gas introduction hole 10 to the sampling passage 11 by negative pressure. Therefore, there is a need for a sample pump 12 capable of generating or exceeding the negative pressure. Note that the sample pump 12 for sampling the exhaust gas of the vehicle as in the present embodiment needs to be capable of generating a large negative pressure in order to simulate the driving state of the vehicle from a flat ground state to a high ground state. is there. The pressure change according to the simulation can be freely performed by the pressure control valve 24 and the gas flow rate control valve 19.

FIG. 3 is a sectional view from the side of the impinger assembly 15 according to the present invention. FIG. 4 is a sectional view of the impinger assembly 15 from the front, and FIG. 5 is a plan view. As shown in FIG. 3, the impinger assembly 15 includes a plurality of impinger 30, a basket 31 in which the impinger 30 can be fixed and stored, and a carrying handle 32 for storing the basket 31.
It consists of an ice bath 33 with.

The impinger 30 is usually made of (colored) glass or the like, and has an absorbent storage section 34, an expansion section 35 for preventing overflow of the absorbent during gas bubbling, a gas introduction pipe 36, an absorption residual gas, and the like. Gas reservoir 37,
And a gas discharge pipe 38. If the end portions 36a, 38a of the gas introduction pipe 36 and the gas discharge pipe 38 are of a rubbing type, the connection is easy and the sealing property is good.

The ice bath 33 includes the impinger 3.
This is for preventing the temperature of the absorbing liquid in 0 from rising or falling due to gas absorption heat or the like, and for operating in a constant temperature state. The handle 32 can be folded when not in use. A plate spring 44 for fixing the gas introduction pipe 36 and the gas discharge pipe 38 is attached to the upper surface of the ice bath 33. The leaf spring 44 also has the effect of further improving the sealing performance of the sliding type.

On the other hand, as shown in FIG. 4, the basket 31 is made of plastic, coated metal wire or the like, and is used to hold the plurality of impingers 30 in a fixed manner so as to hold the absorbent storage portion 34. Lattice frame 39,
An arc-shaped frame 40 for supporting the lower surface of the inflatable portion 35, a handle 41 for carrying, an outer peripheral frame 42 constituting the outer shape of the basket 31, and an inner wall of the ice bath 33 for fixing the basket 31 itself. It consists of a fixed frame 43. In addition, it is also preferable to form the lattice-shaped frame 39 and the bow-shaped frame 40 by punching a flat plate or the like.

Also, as shown in FIG.
There are eight places for setting the blank impinger 45, and a place for setting the blank impinger 45 is also defined.

The impinger assembly 15 according to the present invention.
Connects at least two impinger 30 in series with the sampling passage 11 in order to improve the gas measurement accuracy. However, an increase in the number of the impinger 30 causes an increase in the passage resistance. Therefore, considering conditions such as measurement accuracy, measurement speed, and miniaturization of the capacity of the sample pump 12, the number of the impinger 30 connected in series is most preferably two.

In the case of the two series, the first impinger 30 absorbs about 90% or more of the gas to be measured, and the second impinger 30 absorbs about 90% or more of the unabsorbed gas. . Therefore, at least 9
9% of the gas will be sampled. Such distribution of the gas absorption ratio to each impinger 30 is experimentally performed in advance by the pressure control valve 24 and the gas flow control valve 1.
If the appropriate opening of the valve of No. 9 is determined, it can be easily performed.

Next, a gas sampling method according to the present invention will be described. In FIG. 1, the vehicle 1 is driven in a predetermined test mode. At this time, the exhaust gas discharged from the exhaust tail pipe 2 is diluted in the mixing section 8 by the air from the dilution air inlet 7, and forms a stable flow by the action of the critical flow venturi 9 and the blower 5.

The following preparatory operations are performed in the above stable flow state. That is, a dummy impinger (not shown) is connected to the sampling passage 11 instead of the impinger assembly 15, and the first three-way valve 14 and the second three-way valve 16 are turned on to drive the sample pump 12 (see FIG. 2).
By this operation, the gas is supplied to the sampling gas inlet 10.
Flows into the sampling passage 11 through Note that the drive source of the sample pump 12 may be any type such as electric drive or hydraulic drive.

Next, the gas flow rate in the sampling passage 11 is adjusted. This adjustment can be performed by monitoring the flow meter 18 and determining the opening of the gas flow control valve 19 and the pressure control valve 24. Each valve may be manual or automatic. It is also preferable to refer to the pressure value detected by one or both of the first pressure gauge 13 and the second pressure gauge 20 together with the flow meter 18. In this way, after determining the opening of the valve that can obtain the target gas flow rate, the first three-way valve 14 and the second three-way valve 1
After turning off the sample pump 6, the sample pump 12 is stopped. Since the gas sampling device according to the present invention is provided with the flow meter 18, the first pressure gauge 13, and the second pressure gauge 20, it is possible to determine whether the gas sampling status is normal based on the indicated values. You can figure out. Further, in the present apparatus that can easily and accurately adjust the pressure in the sampling passage 11, the amount of the absorbing liquid in the impinger 30 can be changed according to the trapped gas.

After the above preliminary operation is completed, an operation of gas sampling is performed. First, the dummy impinger is removed. Then, the basket 31 in which the impinger 30 for measurement and the blank impinger 45 are set is placed in the ice bath 33, and the gas introduction pipe 36 and the gas discharge pipe 38 are connected to the sampling passage 11 using the leaf spring 44. The impinger 30 and the blank impinger 45 are previously filled with an absorbing liquid capable of absorbing the target gas. In addition, water, ice, and the like are put in the ice bath 33 to stabilize gas absorption conditions (temperature). As shown in FIGS. 3 to 5, eight impinger 30 are set, and two impinger 30 are connected in series to form four series. Therefore, four measurement samples can be obtained by one sampling.

An example of gas absorption by the above absorbing solution will be described.
For example, when it is desired to collect carbonyl compounds, a solution of 2,4-dinitrophenylhydrazine in acetonitrile is used as the absorbing solution. Also, sulfuric acid is added as an acid catalyst. 2,4-Dinitrophenylhydrazine and the carbonyl compound undergo a chemical reaction to form a hydrazone compound as shown in the following chemical formula 1. The obtained hydrazone compound is separated from unreacted 2,4-dinitrophenylhydrazine by liquid chromatography, and can be quantitatively and qualitatively determined by ultraviolet spectroscopy.

[0030]

Embedded image

Next, actual sampling is started. First
The three-way valve 14 and the second three-way valve 16 are turned off as described above, that is, both ends of the impinger 30 are open to the atmosphere. Then, at the same time when the sample pump 12 is driven, the second
The three-way valve 16 is turned on to communicate the sampling passage 11. Thereafter, after the first predetermined time has elapsed, the first
The three-way valve 14 is switched on. As a result, exhaust gas is introduced into the impinger 30 instead of the atmosphere, absorption of the target gas is started by bubbling, and measurement by the dry gas meter 21 is started. After the second predetermined time has elapsed after the driving of the sample pump 12, the second three-way valve 16 is turned on to communicate the sampling passage 11. After this,
If the first three-way valve 14 is turned on after the third predetermined time has elapsed, more accurate sampling can be performed.

The first predetermined time is defined as the time when the negative pressure generated by the operation of the sample pump 12 is applied to the gas outlet side of the first three-way valve 14 through the second three-way valve 16 and the two impinger 30 connected in series. It is time to reach. This first predetermined time is determined by the second three-way valve 16, the impinger 3
It changes depending on the degree of resistance of 0. Instead of the first predetermined time, the display pressure of the second pressure gauge 20 is the display pressure of the first pressure gauge 13 and the resistance value of the passage between the gas inlet side of the second three-way valve 16 and the gas outlet side of the first three-way valve 14. When the value becomes lower than the sum of the above, the same result can be obtained even if the first three-way valve 14 is switched on. The second predetermined time is a time until the negative pressure generated by driving the sample pump 12 reaches the gas outlet side of the second three-way valve 16, and the third predetermined time is a time when the negative pressure is This is the time from the second three-way valve 16 to the gas outlet side of the first three-way valve 14 through the impinger assembly 15. Therefore, the first predetermined time is substantially equal to the second predetermined time plus the third predetermined time.

By the above operation, the sample gas can be stably absorbed by the impinger 30. Therefore, there is no trouble such that the pressure before and after the impinger 30 is reversed and measurement failure occurs. Further, if the present apparatus is used, it is possible to check the pressure leak related to the impinger assembly 15 using the first pressure gauge 13 and the second pressure gauge 20.

With respect to the impinger assembly 15, each impinger 30 is filled with the absorbing liquid at another place.
This is set in the basket 31, and the ice bath 33
If it is set in the sampling state, it is convenient because there is no need to perform the complicated setting as described above at the sampling site. If the basket 31 is removed from the ice bath 33 after the sampling is completed, the impinger 30 can be stood up like a test tube stand, which is convenient. In addition, the impinger 30 after sampling is completed.
Even when a warm bath is performed as a post-treatment, the basket 31 can be carried to the warm bath apparatus as it is, and the warm bath can be easily performed.

According to the above-described method, gas sampling is performed for a certain period of time.
4 is turned off and the second three-way valve 16
Is turned off, and the sample pump 12 is stopped almost simultaneously,
The detection value of the dry gas meter 21 is read, and the impinger 30 is taken out. Therefore, the collection can be completed by the impinger 30 without fail until the sampling is completed. This principle is the same as at the start of gas sampling.

Using the above results, the concentration C of the sampling gas is obtained by the following equation (2). Further, the weight of the sampling gas can be obtained from the concentration C. In the equation (2), K: correction coefficient for each molecular weight C _R ; concentration of standard sample A _S1,2 ; sample area value of first and second impinger AV _S1,2 ; sample volume of first and second impinger a _R; detecting pressure in the second pressure gauge Q;; area value P _a of the standard sample molecular weight ratio V _SE; sampling flow rate (dry gas meter 21 detected value) T _EF; sampling gas temperature (gas temperature measuring device 2
K and Q are numerical values obtained in advance for each gas type.

[0037]

(Equation 2)

By adjusting the opening of the pressure control valve 24,
If the PA value is smaller than the pressure in the sampling gas introduction hole 10 and approximates to the atmospheric pressure, the sampling accuracy can be further improved.

[0039]

As described above, the method according to the present invention comprises:
First, the first and second three-way valves are turned off, and the second three-way valve is turned on almost simultaneously with the start of the operation of the sample pump. After a lapse of time, the first three-way valve is switched on, so that the pressure before and after the gas collection unit does not reverse.
Accordingly, troubles such as sampling failure do not occur, and the detection accuracy of the dry gas meter can be improved.

If the predetermined time is a time until the gas outlet side pressure of the second three-way valve becomes lower than the inlet side pressure of the first three-way valve, the outlet pressure of the gas collecting portion is Sampling can be started in a state where is set lower than the inlet pressure. Therefore, the sampling accuracy can be further improved.

In the apparatus of the present invention, a first three-way valve is installed on the gas inlet side of the gas collecting part, and a second three-way valve is installed between the gas outlet side and the sample pump. Since the branch pipe provided with the pressure regulating valve is provided between the second three-way valve and the sample pump, the outlet pressure and the inlet pressure can be appropriately adjusted by the above-described method. Therefore, troubles such as sampling failure do not occur, and the sampling accuracy can be improved.

Further, by adding a first pressure gauge to the gas inlet side of the first three-way valve and a second pressure gauge to the gas outlet side of the second three-way valve, the pressure in the sampling passage can be reduced. Can be measured. Therefore, the pressure of the gas flowing through these sampling passages can be adjusted to a value suitable for sampling. Further, if the first and second pressure gauges are added as described above, it is possible to perform a pressure correction of the obtained numerical value and obtain a highly accurate analysis result.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas sampling device according to the present invention.

FIG. 2 is an enlarged view of a portion surrounded by a broken line in FIG. 1;

FIG. 3 is a side sectional view of the impinger assembly according to the present invention.

FIG. 4 is a sectional view from the front of the same.

FIG. 5 is a plan view of the same.

FIG. 6 is a schematic diagram of a CVS device using a conventional CFV.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Exhaust tail pipe, 5 ... Blower, 6 ... Gas passage, 7 ... Dilution air inlet, 9 ... Critical flow venturi, 10 ... Sampling gas inlet, 11 ... Sampling passage, 12 ... Sample pump, 13: first pressure gauge, 14: first three-way valve, 15: impinger assembly (gas collection unit), 16: second three-way valve, 18: flow meter,
19: gas flow control valve, 20: second pressure gauge, 21:
Dry gas meter, 23 ... branch pipe, 24 ... pressure control valve, 3
0 ... impinger, 31 ... basket, 32 ... handle,
33 ... ice bath, 39 ... lattice frame, 40 ... bow frame, 4
1 ... Handle, 42 ... Peripheral frame, 43 ... Fixed frame, 44 ... Leaf spring, 45 ... Blank impinger.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideo Furumoto 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Haruko Kabuki 1-4-1 Chuo, Wako-shi, Saitama Inside the Honda R & D Co., Ltd. (72) Kaoru Nakade, Inventor Kaoru 1-4-1, Chuo, Wako-shi, Saitama Prefecture Inside the Honda R & D Co., Ltd. (56) References JP-A-55-74438 (JP, A) JP-A-4-270945 (JP, A) JP-A-6-34500 (JP, A) JP-A-63-73135 (JP) JP, A) JP-A-55-65133 (JP, A) JP-A-61-124849 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 1/00-1/34 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A target gas is guided to a gas sampling device, the gas is absorbed by a gas collecting portion provided in the gas sampling device, and the gas flow rate is measured by a flow meter provided downstream of the gas collecting portion. Further, the gas flow rate is controlled by a flow rate control valve provided downstream of the flow meter, and gas is sucked by a sample pump provided downstream of the flow rate control valve. On the inlet side, a first three-way valve that opens the sampling passage when on, closes the sampling passage on the inlet side when off and opens the sampling passage on the outlet side to the atmosphere when off, and installs the gas collection unit and the flow Between the meter and the meter, a second three-way valve that opens the sampling passage when on, closes the sampling passage on the outlet side when off, and opens the sampling passage on the inlet side to atmosphere is installed. Further, a branch pipe having a pressure control valve for adjusting the pressure of the sampling passage by sucking outside air is provided between the flow rate control valve and the sample pump, and first, the first and second three-way valves are turned off. A gas sampling method, wherein after the sample pump is operated, the second three-way valve is turned on, and after a predetermined time, the first three-way valve is turned on to start gas sampling. 2. The method according to claim 1, wherein the predetermined time is a time required for the gas outlet pressure of the second three-way valve to drop by a predetermined pressure from the inlet pressure of the first three-way valve. The gas sampling method according to 1. 3. A target gas is guided to a gas sampling device, the gas is absorbed by a gas collection unit provided in the gas sampling device, and the gas flow rate is measured by a flow meter provided downstream of the gas collection unit. A gas sampling device that controls a gas flow rate with a flow rate control valve provided downstream of the flow meter and sucks gas with a sample pump provided downstream of the flow rate control valve; On the gas inlet side, a first three-way valve that opens the sampling passage when on, closes the sampling passage on the inlet side and opens the sampling passage on the outlet side when off, and installs a first three-way valve on the gas inlet side, Between the flow meter and the flow meter, open the sampling passage when on, close the sampling passage on the outlet side when off, and open the sampling passage on the inlet side to the atmosphere. And a branch pipe provided with a pressure control valve for adjusting the pressure of the sampling passage by sucking outside air between the flow rate control valve and the sample pump. And a gas sampling device. 4. A first pressure gauge is added to a gas inlet side of the first three-way valve, and a second pressure gauge is added to a gas outlet side of the second three-way valve. Item 3
The gas sampling device according to item 1.