JP2011095229A - Dilution air refining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce to the utmost, the ratio of an N<SB>2</SB>O concentration in dilution air to an N<SB>2</SB>O concentration in exhaust gas diluted by the dilution air by removing N<SB>2</SB>O in the dilution air, and to thereby improve measurement accuracy of the N<SB>2</SB>O concentration in the exhaust gas. <P>SOLUTION: This dilution air refining device 3 used in an exhaust gas sampling analysis system 100 for measuring components included in the diluted exhaust gas acquired by diluting engine exhaust gas by the dilution air includes: a heating part 33 for heating the dilution air collected from the atmosphere; a catalyst part 34 for converting N<SB>2</SB>O included in the heated dilution air into N<SB>2</SB>or NO<SB>X</SB>; and an NO<SB>X</SB>removal part 38 provided on the downstream of the catalyst part, for removing NO<SB>X</SB>included in the dilution air. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an air purification apparatus for dilution used in an exhaust gas sampling analysis system.

Conventionally, as an air purification apparatus for dilution used in an exhaust gas sampling analysis system, as shown in Patent Document 1 or 2, an oxidation catalyst (Pd system, Pt system, etc.) is used to oxidize CO, HC, NO _X, etc. together is, it is to adsorb and remove the NO _X by NO _X removal agent.

In recent years, dinitrogen monoxide (N ₂ O) has attracted attention as a greenhouse gas, and N ₂ O contained in exhaust gas is no exception, and it is necessary to analyze the concentration of N ₂ O contained in exhaust gas. It is happening.

In the exhaust gas analysis using the dilution sampling method in the exhaust gas sampling analysis system, the component concentration in the dilution air is measured, the component concentration in the diluted exhaust gas is measured, and the difference between the measurement results is obtained. Thus, the background is corrected and the component concentration in the exhaust gas is calculated. The same technique is used when measuring the N ₂ O concentration in the exhaust gas.

However, the dilution air collected from the atmosphere already contains about 300 ppb of N ₂ O, and especially when the concentration of N ₂ O contained in the exhaust gas is close to or lower than that, The measurement error of the N ₂ O concentration in the dilution air greatly affects the N ₂ O concentration in the exhaust gas after background correction, and as a result, the measurement accuracy of the N ₂ O concentration in the exhaust gas is deteriorated. There is. That is, there is a problem that the ratio of the N ₂ O concentration of the dilution air to the N ₂ O concentration in the diluted exhaust gas is large.

JP-A-6-3232 Japanese Patent Laid-Open No. 10-19744

The present invention removes the N _{2 O} in the dilution air, as much as possible the proportion of N _{2 O} concentration of the dilution air to N _{2 O} concentration in the exhaust gas diluted by the dilution air small Therefore, it is a main intended issue to improve the measurement accuracy of the N ₂ O concentration in the exhaust gas.

That is, the dilution air purifying apparatus according to the present invention is a dilution air purifying apparatus used in an exhaust gas sampling analysis system for diluting engine exhaust gas with dilution air and measuring components contained in the diluted exhaust gas. A heater for heating the dilution air collected from the catalyst, a catalyst part for converting N ₂ O contained in the dilution air heated by the heater into N ₂ or NO _X , and downstream of the N ₂ O catalyst part provided, characterized in that it comprises, a NO _X removal unit for removing NO _X contained in the dilution air.

According to thus constituted present invention, the ratio of N _{2 O} concentration of the dilution air for removing the N _{2 O} in the dilution air, N _{2 O} concentration in the exhaust gas diluted by the dilution air Can be made as small as possible, and the measurement accuracy of the N ₂ O concentration in the exhaust gas can be improved.

1 is a schematic perspective view of an exhaust gas sampling analysis system according to an embodiment of the present invention. It is a figure which shows the structure of the air purification apparatus for dilution of the embodiment. It is a schematic diagram showing a correction result in the presence of N _{2 O} removal dilution air.

  Hereinafter, an embodiment of an exhaust gas sampling analysis system using a dilution air purifier according to the present invention will be described with reference to the drawings.

  The exhaust gas sampling analysis system 100 according to this embodiment is of a dilution sampling system, and engine exhaust gas (hereinafter referred to as “exhaust gas”) collected from the automobile 200 is diluted several times with dilution air purified from the atmosphere. Thus, the concentration is measured. Hereinafter, in the present embodiment, a description will be given of a constant volume, constant volume dilution sampling method in which the exhaust gas is sampled and diluted with dilution air to obtain a constant known flow rate.

  Specifically, as shown in FIG. 1, the exhaust gas is diluted with exhaust gas (hereinafter referred to as “diluted exhaust gas”) by introducing a total amount of exhaust gas and dilution air into the apparatus and controlling the combined total flow rate to be always constant. , "Diluted exhaust gas") is supplied to the constant volume sampling device 2 with a constant volume sampling device 2 that collects a part of the exhaust gas in a collection bag at a constant flow rate, and dilution air purified by removing impurities in the atmosphere. And a gas analyzer 4 for analyzing the concentration of a predetermined component (for example, HC, CO, etc.) in the diluted exhaust gas collected by the collection bag of the constant volume sampling device 2. Yes.

  The constant volume sampling device 2 is connected to the exhaust pipe 200H of the automobile 200 mounted on the chassis dynamo 300, and the exhaust gas introduction line 21 to which the dilution air supply pipe 3H of the dilution air purification device 3 is introduced and connected. The diluted exhaust gas distribution line 23 provided downstream of the exhaust gas introduction line 21 and having a constant flow mechanism 231 for flowing the diluted exhaust gas stirred and mixed by the cyclone 22 at a constant flow rate. The dilution exhaust gas collecting line 24 for separating the diluted exhaust gas from the diluted exhaust gas distribution line 23 and the dilution for separating the dilution air from the dilution air supply pipe 3H of the dilution air purifier 3 Air sampling line 25.

  The constant flow rate mechanism 231 includes a venturi pipe 231a provided on the diluted exhaust gas distribution line 23 and a turbo blower 231b provided downstream of the venturi pipe 231a.

  The diluted exhaust gas collection line 24 has one end provided in the diluted exhaust gas distribution line 23, a diluted exhaust gas collection pipe 241 provided on the diluted exhaust gas collection pipe 241, and the diluted exhaust gas collection pump 242. And a diluted exhaust gas bag 243 for storing the diluted exhaust gas collected by the above. The diluted exhaust gas sampling pipe 241 is provided on the upstream side of the constant flow rate mechanism 231.

  The dilution air sampling line 25 has a dilution air sampling pipe 251 provided at one end in the dilution air supply pipe 3H, and a dilution air sampling pump 252 provided on the dilution air sampling pipe 251. And a dilution air bag 253 for storing the dilution air collected by the dilution air sampling pump 252.

  Then, so-called bag measurement is performed by the gas analyzer 4 using the diluted exhaust gas bag 243 of the diluted exhaust gas sampling line 24 and the diluted air bag 253 of the dilution air sampling line 25.

The dilution air purifying apparatus 3 removes CO, HC, NO _{x and the} like in the dilution air in order to stabilize the low concentration of the background in the exhaust gas analysis. In this dilution air purifier 3, CO, HC, as a method for removing NO is, CO in the diluted air, HC, the catalytic oxidation method to convert the NO to CO ₂ and _{H 2} O and NO ₂ adopted In addition, NO ₂ produced by oxidation of NO is adsorbed using a NO _X adsorbent. Further, the NO _X adsorbent also contains an oxidant, and the unconverted NO is oxidized to NO _X and adsorbed.

As shown in FIG. 2, the specific configuration of the dilution air purifying device 3 includes a suction pump 32 that introduces dilution air from the outside through the intake filter 31 and the suction pump 32. The heater 33 for heating the diluted air to about 400 degrees, and the catalyst unit 34 using Pt, Pd system or Cu, Mn system for burning HC and CO in the dilution air heated by the heater 33 A cooling unit 37 that cools the dilution air that has passed through the catalyst unit 34 and the heat exchanger 35 and the three-way solenoid valve 36 that are provided downstream of the catalyst unit 34, and a dilution unit that is cooled to, for example, 25 degrees by the cooling unit 37. And an NO _X adsorber 38 that adsorbs and removes NO ₂ in the air. The dilution air that has passed through the NO _X adsorber 38 is supplied to the constant volume sampling device 2 through the dilution air supply pipe 3H.

Therefore, the gas analyzer 4 of the present embodiment analyzes the concentration of the N ₂ O component in the diluted exhaust gas, and the dilution air purifier 3 removes N ₂ O in the dilution air. ₂ O removal part 3A is provided. The _{N 2} O removal section 3A, and _{N 2} O catalyst unit for converting the _{N 2} or NO _X by reduction or oxidation of _{N 2} O, and NO _X removal unit for removing the NO _X produced by the _{N 2} O catalytic unit It consists of.

The N ₂ O catalyst portion is included in the catalyst portion 34, and is configured by, for example, supporting Pt or Pd on zeolite. Further, the NO _X removing unit constituting the N ₂ O removing unit 3A is configured by using the NO _X adsorber 38.

Next, N ₂ O concentration measurement using the thus configured exhaust gas sampling analysis system 100 will be described with reference to FIG.

When the dilution air purifier 3 does not have the N ₂ O removing unit 3A, the N ₂ O concentration in the dilution air obtained by the dilution air bag 253 is about 300 [ppb] (N ₂ O contained in the atmosphere). Density average value). When _{N 2} O concentration in the dilution in the exhaust gas obtained by diluting the exhaust gas bag 243 at this time it is assumed to be approximately 560 [ppb], the results of background correction, _{N 2} O concentration in the exhaust gas, about 260 [ppb] It becomes. However, large proportions of N _{2 O} concentration in the dilution air for N _{2 O} concentration in the diluted exhaust gas is greatly affected the measurement error of the N _{2 O} concentration in the dilution air is applied to the N _{2 O} concentration in the exhaust gas As a result, the measurement accuracy of the N ₂ O concentration in the exhaust gas obtained by the background correction is lowered.

On the other hand, when the N ₂ O removing unit 3A is provided as in the present embodiment, the N ₂ O concentration in the dilution air obtained by the dilution air bag 253 is reduced to, for example, about 30 [ppb]. The N ₂ O concentration in the diluted exhaust gas obtained by the diluted exhaust gas bag 243 is about 290 [ppb], and as a result of background correction, the N ₂ O concentration contained in the exhaust gas is about 260 [ppb]. At this time, N _{2 O} concentration ratio can be reduced in, N _{2 O} concentration of the measurement error in the exhaust gas of the N _{2 O} concentration in the dilution air dilution air for N _{2 O} concentration in the diluted exhaust gas As a result, the measurement accuracy of the N ₂ O concentration in the exhaust gas obtained by background correction can be improved.

According to the exhaust gas sampling analysis system 100 of the present embodiment configured as described above, prior to diluting the exhaust gas with dilution air, by removal of N _{2 O} from the dilution air, in the diluted exhaust gas N ₂ the ratio of N _{2 O} concentration in the dilution air to O concentration as much as possible can be made small, to reduce the background variation of the N 2 _O concentration, to improve the measurement accuracy of the N _{2 O} concentration in the exhaust gas be able to.

The present invention is not limited to the above embodiment.
For example, the constant volume sampling device is used in the embodiment, but a back mini-diluter device that collects a part of the exhaust gas and dilutes it at a constant ratio may be used.
In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

100 ... exhaust gas sampling measurement system 2 ... constant volume sampling device 3 ... dilution air purifier 3A ... _{N 2} O removal unit 33 ... heater 34 ... catalyst 38 ... NO _X removal section

Claims (1)

An air purification device for dilution used in an exhaust gas sampling analysis system for diluting engine exhaust gas with dilution air and measuring components contained in the diluted exhaust gas,
A heater for heating dilution air collected from the atmosphere;
An N ₂ O catalyst unit for converting N ₂ O contained in the dilution air heated by the heater into N ₂ or NO _X ;
A dilution air purification apparatus, comprising: a NO _X removal section that is provided downstream of the N ₂ O catalyst section and removes NO _X contained in the dilution air.