JPS5950930B2 - Method and device for measuring SO↓2 concentration by fluorescence analysis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring method and apparatus that employs a novel base stabilization mechanism in measuring 502 concentration using a fluorescence method.

SO_2 molecules have three absorption wavelengths in the ultraviolet range, and when excited by ultraviolet light in any of these wavelength ranges, they generate fluorescent ultraviolet light.

The present invention aims to eliminate fluctuations in the measured value base due to special background phenomena in a method for determining SO_2 concentration by measuring the intensity of fluorescent ultraviolet light emitted by SO_2 in a sample gas. .

Therefore, in order to elucidate the cause of base fluctuations, the inventors first conducted various investigations into the relationship between zero gas components and base stability.

As a result, first, the background level of zero gas consisting of No or rare gases is relatively large and unstable, whereas in the case of air from which SO_2 has been removed, the background level is relatively small and stable. confirmed. If the cause of this is considered in particular to the difference between No and air, it is due to the presence or absence of a component other than nitrogen, that is, oxygen, which occupies most of the air. From the above perspective, FIG. 1 corresponds to high purity N2 gas (99.99% or more).

. The relationship between the mixing ratio and the background value converted to the SO_2 concentration to be measured is measured and shown in a graph. According to this graph, the 00 concentration is about 0 to 1
The background value in the range of about 0.0% is about 1.6ppμ when 00 is not mixed, then it reaches about 3ppn, then it drops rapidly in 5 hours, and after passing through a metamorphosis region of 00 concentration of 1 to 3%, the background value decreases. It can be seen that there is a flat and extremely gradual decline below approximately 1.5p Uzani. The reason why the 02 concentration in the gas dominates the background value still needs to be clarified in the future, but given that the background value drops particularly sharply in the region of trace 02 concentration, the following It can be thought of as follows. In other words, wavelengths close to the irradiated ultraviolet rays (190~
The 02 gas, which absorbs 201 nm), partially changes to 03 and acts on minute amounts of background components (for example, hydrocarbons volatilized from the optical paint on the wall of the fluorescent chamber),
In addition to quenching the excited emission, this 03 is 0
2 absorbs the scattered light and leaked light of the irradiated ultraviolet rays, and itself becomes stable in a state where the degree of energy emission at the detection wavelength by the photoelectric element is small. Considering the above, it is 03 that contributes to base stabilization in the zero gas component rather than 02 itself, and in order to confirm this hypothesis, the inventors developed 200 from the beginning. ~450ppn (I tried measuring the background value using 02+03+N2 series zero gas containing 703.

Figure 2 is a graph showing the results of this measurement.
2 In contrast to curve A, which is a transcription of the background curve as it is, curve B is obtained by passing oxygen or air through an ozonizer, and in a fluorescent room, the concentration of 02 is equal to that of A, and the concentration of 02 is approximately proportional to this.
00-450PPn(7)03 concentration 2 is obtained. Comparing curves A and B, when 03 is substantially introduced into the fluorescent room through an ozonizer, the base is stable at a lower level than when 02 is introduced, and the fluctuations in the base curve are also extremely small.
It was confirmed that the 5-base stabilizer plays a major role in stabilizing the base. The present invention attempts to provide an SO2 measurement technique for fluorescence analysis in which the measurement base is stabilized by mixing 03 into the sample gas and the reference gas.

5. FIG. 3 shows a flow path configuration for carrying out the method of the present invention described above. In FIG. 3, 1 is a sample gas inlet, 2 is a filter for sample gas, 3 is a span gas inlet, 4 is a zero gas inlet, and 5 is a filter for zero gas. Each flow path extending from the span gas inlet 3 and the zero gas inlet 4 is selectively connected to one
The main flow path 7 is guided to a stop 8, and is connected to a flow path 9 extending from the sample gas inlet 1 and selectively to a measurement flow path 10. The measuring channel 10 starting from the pot 8 is sequentially equipped with a osmotic dehumidifier 11. A capillary 12, a hydrocarbon cutter 13, a fluorescent chamber 14, and a flowmeter 15 are arranged, and the measured gas passing through the flowmeter 15 is sucked into the pump 18 via vacuum suction channels 16 and 17, and is then discharged into the exhaust flow. Road 1
It is discharged from 9. A vacuum gauge 20 is inserted into the suction flow path 16 and a vacuum regulator 21 is inserted into the downstream suction flow path 17, and these suction flow paths 16 and 17 are connected to the vacuum channel 22 of the osmotic dehumidifier 11. It is connected accordingly. Fluorescence chamber 1 in measurement channel 10
An ozone supply flow path 23 joins the inlet side of 4.

This supply channel 23 is connected from the air inlet 24 to the activated carbon filter 2.
5. Introduce the dust-free and dehumidified air to the ozonizer 28 via the silica gel filter 26 and the capillary 27,
According to the present invention, it is possible to supply zero gas or the like to the fluorescent chamber 14 immediately after mixing 03 in a desired ratio. The excited light emission of body molecules in the fluorescence chamber 14 is detected by a photomultiplier 29, amplified by a signal amplifier 30, and then recorded or read.

31 is a power source for the photomultiplier 29;

FIG. 4 shows a specific configuration regarding ultraviolet irradiation to the fluorescent chamber 14 and the photomultiplier 29.

That is, in this case, the Xe discharge tube 32 is used as the excitation light source.
This was pulse-lit with a cycle of 100 milliseconds and a lighting time of 1 microsecond, and a wavelength of 190 to 230 nm was preferably selected and irradiated into the fluorescence chamber 14 through a slit 33, a lens 34, and a filter 35. . The photomultiplier 29 is configured to detect fluorescence from the excited substance from the side of the fluorescence chamber 14 through similar filters 35'', 35'''' and a lens 34''. The apparatus for implementing the method of the present invention is constructed as described above, and the apparatus is constructed as described above.
The zero gas or span gas introduced into the measurement channel 10 via the gas and 8, or the sample gas introduced into the measurement channel 10 via the gas chamber 8, has zero gas or span gas introduced into the measurement channel 10 through the
The 03-containing air from the 3 supply channel 23 is supplied to the desired 03-containing air to bring the background to a stable low value.
concentration can be achieved.

The osmotic dehumidifier 11 is a device that can remove moisture in gas in the form of molecules by an osmotic method without condensing it.
No losses occur due to dissolution. The dehumidified gas passes through the capillary 12 and is turned to the SO in the cutter 13. It is sent to the fluorescence chamber 14 after aromatic hydrocarbons, which are the main interfering components in fluorescence measurement, are removed. Since the apparatus of the present invention is configured as described above, by setting the flow path resistance of the supply flow path 23 and the flow path resistance of the measurement flow path 10 to a desired ratio, the measurement flow path By constantly adding air or pure oxygen to the gas in 10 at a substantially constant ratio, a stable and low background value can be achieved.

In addition, in FIG. 5, N is connected to the measurement channel 10.

When flowing zero gas consisting of gas at a rate of 1.51/min, the amount of air flowing into the ozone supply channel 23 is set to 20 to 20
It shows the relationship between the ozone concentration % generated in the ozonizer 28, the ozone concentration [Ppn] that has reached the fluorescent chamber 14 based on this, and the oxygen concentration in the fluorescent chamber 14 when the ozonizer 28 is 0 m1/Min. According to these graphs, increasing the air flow rate reduces the ozone generation concentration to a certain extent, but the ozone concentration in the fluorescent room 14 increases almost in proportion to the air volume up to about 450 ppn, as shown in Figure 2. It is clear that a preferred base value within a range can be established.

[Brief explanation of drawings]

Figure 1 is 0. A graph showing concentration-background characteristics, Figure 2 is 0.
0 versus concentration. -0, Drought showing the background characteristics of the system concentration, Figure 3 is a flowchart showing an example of the flow path configuration of the present invention, and Figure 4 shows a specific example of the fluorescence chamber-light detection system in the flow path shown in Figure 3. The schematic cross-sectional view shown in FIG. 5 shows the amount of air in the ozonizer and the fluorescent chamber connected thereto, 0. concentration and 0. It is a graph showing the relationship between concentrations. 1...Sample gas inlet, 3...Span gas inlet, 4...
... Zero gas inlet, 10 ... Measurement channel, 14
...Fluorescent room, 23...0, supply flow path,
29...Photomultiplier, 32...
-Xe discharge tube (excitation light source).

Claims (1)

[Claims] 1. By irradiating ultraviolet rays in the sample gas SO_2 absorption region and measuring the excitation emission intensity of the sample gas,
To determine the SO_2 concentration, O_3 is mixed into the selected reference gas and sample gas to set a reference value corresponding to the zero or span value of the SO_2 concentration, and the light intensity measured for the gas after the O_3 is mixed is used. S by a fluorescence analysis method characterized in that the reference value and the measured value are
O_2 concentration measurement method. 2. The method according to claim 1, wherein the zero gas element constituting the reference gas consists of N_2. 3. The method according to claim 1, characterized in that the sample gas and the reference gas are irradiated with ultraviolet light in pulses. 4. A measurement flow path is provided that connects the downstream end of the sample gas flow path and the reference gas flow path for setting zero or span values to a fluorescence chamber arranged in conjunction with an excitation ultraviolet light source and fluorescence detection means. An apparatus for measuring SO_2 concentration using a fluorescence analysis method, characterized in that a flow path for merging O_3 is connected to the measurement flow path before the fluorescence chamber. 5 O_3 confluence path reaches an ozonizer from the air inlet through at least a filter, and the outlet of the ozonizer is directly connected to the front of the fluorescent room.
Apparatus described in section.