JP2009210452A - Chemiluminescent nitrogen oxide measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemiluminescent nitrogen oxide measuring device for certainly removing NOx such as NO or NO<SB>2</SB>from exhaust gas whose nitrogen oxide concentration has been measured. <P>SOLUTION: The chemiluminescent nitrogen oxide measuring device measures nitrogen oxide concentration from the intensity of chemiluminescence generated by reaction of sample gas containing nitrogen oxide with ozone gas. The exhaust gas after the sample gas and ozone gas are introduced to a measuring cell and the nitrogen oxide concentration has been measured is sequentially passed and exhausted through an ozonolysis catalyst 21, an oxidation adsorbent 22 for oxidizing NO, and an acid gas adsorbent 23 for adsorbing NO<SB>2</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chemiluminescent nitrogen oxide measuring device characterized by exhaust gas treatment means after measuring the nitrogen oxide concentration.

The chemiluminescent nitrogen oxide measuring device measures the nitrogen oxide concentration using chemiluminescence generated by the reaction between a sample gas containing nitrogen oxide (hereinafter also referred to as NOx) and ozone gas. For generation, a silent discharge type ozone generator is used focusing on good generation efficiency.
Moreover, since the exhaust gas after measurement contains unreacted ozone (hereinafter also referred to as O ₃ ) at a high concentration, the exhaust gas is passed through a reducing substance such as activated carbon and various catalysts and converted to oxygen. The method of exhausting is taken.

The ozone generator of silent discharge method in which the air as a raw material, NOx is produced in addition to ozone, many present as NO and NO _2.
In a general ozone decomposition catalyst such as manganese dioxide (MnO ₂ ), NO and NO ₂ leak into the exhaust gas before ozone breaks through. However, NO and NO ₂ are highly corrosive to resin and rubber, and may damage pumps, piping, joints, and the like. For this reason, it is conceivable to take measures such as using those parts that are resistant to corrosion, increasing the amount of catalyst, and increasing the frequency of replacement of parts and catalysts. There is a problem in that the increase in maintenance and the complexity of maintenance work are caused.

Further, when activated carbon having both ozone decomposing ability and NOx adsorption ability is used, NO ₂ is reduced to NO by the reducing action of the activated carbon. However, since the adsorption capacity of activated carbon with respect to NO is small, NO breaks through early, and the same problem as in the case of an ozone decomposition catalyst arises.

  In view of the above points, for example, Patent Document 1 describes a chemiluminescent nitrogen oxide measuring device in which a NOx adsorbent is arranged downstream of an ozonolysis device filled with an ozonolysis catalyst.

JP-A-10-213548 (paragraphs [0016] to [0018], FIG. 1 etc.)

However, in the prior art according to Patent Document 1, an indicator column that changes color in response to ozone and NOx is arranged downstream of the NOx adsorbent, and the deterioration of the ozonolysis catalyst or NOx adsorbent is determined based on the presence or absence of the color change. Therefore, it is not sufficient in terms of removing NO and NO ₂ with certainty.

Therefore, the problem to be solved by the present invention is to provide a chemiluminescent nitrogen oxide measuring device capable of reliably removing NOx such as NO and NO _{2 as} well as ozone from the exhaust gas after measuring the nitrogen oxide concentration. There is.

In order to solve the above-mentioned problem, the invention according to claim 1 is a chemiluminescent nitrogen oxide measuring apparatus for measuring a nitrogen oxide concentration from the intensity of chemiluminescence generated by a reaction between a sample gas containing nitrogen oxide and ozone gas. ,
The exhaust gas after introducing the sample gas and ozone gas into the measuring cell and measuring the nitrogen oxide concentration is in the order of an ozone decomposition catalyst, an oxidizing adsorbent that oxidizes nitrogen monoxide, and an acidic gas adsorbent that adsorbs nitrogen dioxide. It is exhausted through.

  According to the present invention, NOx can be removed over a longer period of time than before, and the replacement frequency and quantity of chemicals such as various adsorbents can be reduced to reduce costs and facilitate maintenance work. . Moreover, the risk of damaging the pump, piping, joints, etc. due to leaked NOx can be reduced, and the life of these devices and parts can be extended.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 is a configuration diagram showing a main part of a chemiluminescent nitrogen oxide measuring apparatus according to this embodiment.
In FIG. 1, reference numeral 10 denotes a measurement cell (reaction tank) for reacting a NOx-containing sample gas with ozone gas and measuring the concentration of NO and further NO ₂ from the chemiluminescence intensity at that time. Here, the ozone gas is supplied from a silent discharge type ozone generator (not shown) using air as a raw material.

On the exhaust side of the measurement cell 10, an ozone decomposition catalyst 21, an oxidizing adsorbent 22, and an acidic gas adsorbent 23 are arranged in this order, and the exhaust gas emitted from the measurement cell 10 is exhausted through these. It is like that.
Here, as the ozone decomposition catalyst 21, a manganese dioxide (MnO ₂ ) -based composite metal oxide catalyst (for example, trade name “calorite”) is used. Further, as the oxidizing adsorbent 22, a gas adsorbent (for example, a trade name “trade name”) which acts to oxidize NO by supporting an oxidizing agent such as potassium permanganate (KMnO ₄ ) on aluminum oxide (Al ₂ O ₃ ). As the acidic gas adsorbent 23, an activated carbon-based gas adsorbent that acts to adsorb NO ₂ by mixing potassium hydroxide (KOH) or the like with activated carbon (for example, the trade name “PuraCarbo”). Is used.

  The ozone decomposition catalyst 21, the oxidizing adsorbent 22, and the acidic gas adsorbent 23 may be filled in separate containers, or the oxidizing adsorbent 22 and the acidic gas adsorbent 23 are filled in the same container in half. You may do it.

Next, FIG. 2 is a configuration diagram (FIG. 2A) of a test apparatus for verifying the effect of the present embodiment, and a graph showing the measurement results of the concentrations of NO ₂ , NO, and O ₃ (FIG. 2B). )).
In the test apparatus shown in FIG. 2 (a), reference numeral 11 denotes a chemiluminescent sample gas measurement NOx meter, which includes the measurement cell 10 and ozone generator (not shown) shown in FIG. It is a normal NOx meter that measures the oxide concentration. Here, the exhaust gas of the sample gas measurement NOx meter 11 (measurement cell 10) is passed through the ozone decomposition catalyst 21, the oxidizing adsorbent 22 and the acidic gas adsorbent 23 in the constant temperature bath 30 at 45 ° C. for exhaustion. It is configured as follows.

In addition, 12 is supplied with a mixed gas of exhaust gas (flow rate is about 1.5 L / min) and dilution gas (flow rate is about 1.5 L / min) from the NOx meter 11 for sample gas measurement. exhaust gas measuring NOx meter for measuring the NOx concentration, 13 is also O ₃ meter exhaust gas measurement which measures the O ₃ concentration in the exhaust gas.
The ozone decomposition catalyst 21 uses about 30 g of “calorite”, the oxidizing adsorbent 22 uses about 75 g of “Purafil”, and the acidic gas adsorbent 23 uses about 75 g of “PuraCarbo”.

In the above configuration, the results of measuring the concentrations of NO ₂ , NO, and O _{3 with} the exhaust gas measuring NOx meter 12 and the exhaust gas measuring O ₃ meter 13 are as shown in FIG.
FIG. 2B shows the relationship between the number of days and the concentration [ppm] of each gas when the sample gas is continuously supplied to the sample gas measuring NOx meter 11 for a long period of time.

Next, FIG. 3 is a configuration diagram of the test apparatus for verifying the effect of the first comparative example (FIG. 3A) and a graph showing the measurement results of the concentrations of NO ₂ , NO, and O ₃ (FIG. 3B). )).
In this first comparative example, the exhaust gas of the sample gas measuring NOx meter 11 is exhausted by passing only through the ozone decomposition catalyst 21 (about 150 g) in the thermostat 30.

FIG. 4 is a block diagram of a test apparatus for verifying the effect of the second comparative example (FIG. 4A) and a graph showing measurement results of NO ₂ , NO, and O ₃ concentrations (FIG. 4B). It is.
In this second comparative example, the exhaust gas of the sample gas measuring NOx meter 11 is exhausted by passing only through the activated carbon (about 150 g) 21 in the thermostat 30.

FIG. 5 is a block diagram of the test apparatus for verifying the effect of the third comparative example (FIG. 5A) and a graph showing the measurement results of the concentrations of NO ₂ , NO, and O ₃ (FIG. 5B). )).
In the third comparative example, the exhaust gas of the NOx meter 11 for measuring the sample gas is exhausted by sequentially passing through the ozone decomposition catalyst (about 30 g) and the oxidizing adsorbent (about 150 g) 22 in the thermostat 30.

  Considering these test results, either the embodiment of the present invention (FIG. 2 (b)) or the first to third comparative examples (FIG. 3 (b), FIG. 4 (b), FIG. 5 (b)). However, it can be seen that ozone has not leaked over a long period of time and is reliably removed.

On the other hand, NO ₂ started to leak from about 30 days in the first comparative example (FIG. 3B) and the second comparative example (FIG. 4B), and the third comparative example (FIG. 5). In (b)), leakage started from about 20 days, whereas in the embodiment of the present invention (FIG. 2 (b)), almost no leakage occurred until around 140 days.

In addition, NO starts to leak from around 40 days in the first comparative example (FIG. 3B), and starts leaking at a high concentration from the beginning of the test in the second comparative example (FIG. 4B). On the other hand, in the embodiment of the present invention (FIG. 2B), almost no leakage occurred until around the 80th day. Note that the NO leakage in the second comparative example (FIG. 4B) may be due to NO ₂ being partially reduced and leaked, but in any case, NOx as a whole is an early stage after the start of the test. It can be said that it is leaking from.
Further, in the third comparative example (FIG. 5B), NO is removed in substantially the same manner as ozone. This is presumably because NO is oxidized to NO ₂ by the action of the oxidizing adsorbent 22, so that it is apparently measured so as not to leak as NO.

In summary, as in this embodiment, ozone is almost completely decomposed by sequentially passing the exhaust gas of the chemiluminescent NOx meter through the ozone decomposition catalyst 21, the oxidizing adsorbent 22 and the acid gas adsorbent 23. At the same time, NO is oxidized by the oxidizing adsorbent 22 to become NO ₂ , and as a result of this NO ₂ being adsorbed by the acidic gas adsorbent 23, NOx is in a state where the amount of leakage is substantially zero over a long period of time compared to each comparative example. Can be maintained.
Further, when focusing on the total amount of NO ₂ and NO, for example, in the first comparative example using only the ozone decomposition catalyst 21 (FIG. 3B), about 60 days have passed after the start of the test and NO ₂ , In contrast to the total amount of NO being about 5 ppm, in this embodiment (FIG. 2B), the total amount of NO ₂ and NO is about 5 ppm after about 180 days have elapsed since the start of the test. Therefore, it has been confirmed that the life of the drug is extended by about three times.

  The ozone decomposition catalyst 21, the oxidizing adsorbent 22, and the acidic gas adsorbent 23 are not limited to the substances described in the embodiment, and substances having an equivalent action may be used.

It is a block diagram which shows the principal part of the chemiluminescent nitrogen oxide measuring apparatus which concerns on embodiment of this invention. It is the block diagram (FIG.2 (b)) which shows the block diagram (FIG.2 (a)) of the test apparatus for verifying the effect of embodiment of this invention, and the measurement result of various gas concentrations. It is a block diagram (Drawing 3 (a)) of a test device for verifying the effect of the 1st comparative example, and a graph (Drawing 3 (b)) which shows a measurement result of various gas concentrations. It is the block diagram (FIG.4 (b)) which shows the block diagram (FIG.4 (a)) of the test apparatus for verifying the effect of a 2nd comparative example, and the measurement result of various gas concentrations. It is a block diagram (FIG.5 (a)) of the test apparatus for verifying the effect of a 3rd comparative example, and the graph (FIG.5 (b)) which shows the measurement result of various gas concentrations.

Explanation of symbols

10: Measurement cell
11: sample gas measurement NOx meter 12: exhaust gas measuring NOx meter 13: exhaust gas measuring _{O 3} meter 21: Ozone decomposition catalyst 22: oxidizing adsorbent 23: acid gas adsorbent 24: activated carbon 30: constant temperature bath

Claims (1)

In the chemiluminescent nitrogen oxide measuring device that measures the nitrogen oxide concentration from the intensity of chemiluminescence generated by the reaction between the sample gas containing nitrogen oxides and ozone gas,
The exhaust gas after introducing the sample gas and ozone gas into the measuring cell and measuring the nitrogen oxide concentration is in the order of an ozone decomposition catalyst, an oxidizing adsorbent that oxidizes nitrogen monoxide, and an acidic gas adsorbent that adsorbs nitrogen dioxide. A chemiluminescent nitrogen oxide measuring apparatus which is exhausted by passing through.

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