JP2008175626A - Ozone measuring method and ozone measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein an ozone concentration in sample gas cannot be measured accurately if a light quantity of an ultraviolet lamp is fluctuated, in ozone measurement for measuring respectively ultraviolet absorbance of the sample gas and ultraviolet absorbance of reference gas, and operating the ozone concentration in the sample gas from both ultraviolet absorbances. <P>SOLUTION: When a changing rate of the ultraviolet absorbance of the reference gas, namely, a changing rate of the light quantity of the ultraviolet lamp, exceeds a prescribed threshold, operation of the ozone concentration in the sample gas from each ultraviolet absorbance of the sample gas and the reference gas is suspended. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ozone measuring method and apparatus for measuring ozone concentration in the atmosphere and the like. More specifically, the ultraviolet absorbance of a sample gas and the ultraviolet absorbance of a reference gas are measured, and the sample gas is determined from the difference between these ultraviolet absorbances. The present invention relates to an ozone measuring method and apparatus for determining the ozone concentration in the inside.

  As an ozone measuring apparatus based on the ultraviolet absorption method for measuring the ultraviolet absorbance of the sample gas and the ultraviolet absorbance of the reference gas and obtaining the ozone concentration in the sample gas from the difference between the two ultraviolet absorbances, there has conventionally been an instrument having the configuration shown in FIG. Yes (see, for example, Patent Document 1). 5, 2 is a sample gas inlet, 4 is a sample gas flow pipe, 6 is a three-way switching valve, 8 is a bypass pipe, 10 is an ozone decomposer, 12 is a measurement cell, 14 is an ultraviolet lamp, 16 Is a detector, 18 is a comparison operation circuit, 20 is a flow meter, 22 is a pump, 24 is a pipe, and 26 is a sample gas outlet. The ozone concentration measurement by the apparatus of FIG. 5 is performed according to the following procedure.

  (1) By operating the pump 22, the sample gas is sucked into the flow pipe 4 from the sample gas introduction port 2 at a constant flow rate, and the sample gas is introduced into the cell 12 without passing through the bypass pipe 8 by operating the three-way switching valve 6. .

  (2) The sample gas in the cell 12 is irradiated with ultraviolet rays having a specific wavelength from the ultraviolet lamp 14. Thereby, ultraviolet rays proportional to the concentration of coexisting components having absorption in ozone and other ultraviolet rays in the sample gas are absorbed by the sample gas. The attenuated ultraviolet light is detected by the detector 16 and converted into an electric signal corresponding to the intensity, and stored in the comparison operation circuit 18.

  (3) By switching the three-way switching valve 6 and flowing the sample gas to the bypass pipe 8, the sample gas is passed through the ozonolysis device 10 to prepare a reference gas not containing ozone, and this reference gas is introduced into the cell 12. Repeat the same measurement. In this case, since only ozone in the sample gas is decomposed by the ozone decomposer 10, ultraviolet rays proportional to the concentration of coexisting components other than ozone are absorbed. The attenuated ultraviolet light is detected by the detector 16 and converted into an electric signal corresponding to the intensity, and stored in the comparison operation circuit 18.

  (4) The comparison calculation circuit 18 compares the ultraviolet intensity electrical signal attenuated by ozone and other coexisting components with the ultraviolet intensity electrical signal attenuated only by the coexistence components, and the difference is an electricity corresponding to the ozone concentration. Output as a signal. By repeating the above operation, the ozone concentration in the sample gas is intermittently measured.

  In the ozone measuring apparatus described above, the sample gas or reference gas is irradiated with ultraviolet rays having a specific wavelength from an ultraviolet lamp (usually a low-pressure mercury lamp). If the light quantity of the ultraviolet lamp fluctuates in this way, the ozone concentration in the sample gas cannot be measured correctly.

  On the other hand, as shown in FIG. 5, a detector 28 is provided only for detecting the light amount of the ultraviolet lamp 14, and the detector 28 monitors whether or not the light amount of the ultraviolet lamp 14 is stable. Thus, the above-described problem that the light amount of the ultraviolet lamp fluctuates is addressed.

  Further, it has been proposed to cope with the above-mentioned problem of fluctuation of the light quantity of the ultraviolet lamp by turning off the ultraviolet lamp for a certain period of time when the light quantity of the ultraviolet lamp is disturbed and then turning it on again (Patent Document). 2).

JP-A-7-159313 Japanese Utility Model Publication No. 5-90349

  However, the above-described method of providing a detector only for detecting the amount of light of the ultraviolet lamp has a problem that the cost of the apparatus increases due to the provision of the detector. In addition, the method of Patent Document 2 described above has a problem that the ozone concentration cannot be measured while the ultraviolet lamp is turned off.

  The present invention has been made in view of the above-described circumstances. When the light quantity of the ultraviolet lamp fluctuates without providing a detector only for detecting the light quantity of the ultraviolet lamp and without turning off the ultraviolet lamp, An object of the present invention is to provide an ozone measuring method and a measuring apparatus that solve the above-mentioned problem that ozone concentration in gas cannot be measured correctly.

  As a result of various studies conducted by the present inventors to achieve the above object, when the ozone concentration in the sample gas is calculated from the ultraviolet absorbance of the sample gas and the reference gas, the reference gas does not contain ozone. Therefore, the UV absorbance of the reference gas and the UV lamp light quantity are well correlated, and when the UV lamp light quantity varies, the UV absorbance of the reference gas changes in response to the above-mentioned UV lamp light quantity fluctuation. It has been found that when the rate of change in UV absorbance increases, it can be determined that the amount of light from the UV lamp fluctuates greatly and the ozone concentration in the sample gas cannot be measured correctly. If the rate of change in UV absorbance of the reference gas exceeds a certain threshold, do not calculate the ozone concentration from both UV absorbances, that is, do not acquire the measured ozone concentration. Thus, it was found that the ozone concentration in the sample gas can always be measured correctly even when the light quantity of the ultraviolet lamp fluctuates.

  The present invention was made on the basis of the above findings, and in the ozone measuring method for measuring the ultraviolet absorbance of the sample gas and the ultraviolet absorbance of the reference gas, respectively, and calculating the ozone concentration in the sample gas from both ultraviolet absorbances, Provided is an ozone measuring method characterized in that, when the rate of change in UV absorbance of a reference gas exceeds a predetermined threshold, the ozone concentration in the sample gas is not calculated from both UV absorbances.

  The present invention also relates to an ozone measuring apparatus that measures the ultraviolet absorbance of the sample gas and the ultraviolet absorbance of the reference gas, and calculates the ozone concentration in the sample gas from these ultraviolet absorbances, and the rate of change in the ultraviolet absorbance of the reference gas. The ozone measuring device is characterized in that when the value exceeds a predetermined threshold value, the ozone concentration in the sample gas is not calculated from the both ultraviolet absorbances.

  The ozone measuring apparatus of the present invention may have a configuration in which the sample gas and the reference gas are alternately introduced into one measuring cell as shown in FIG. 5, and two measuring cells are arranged in one cell. The sample gas may have a configuration in which a reference gas is introduced into the other cell, or may have another configuration.

  The ozone measuring method and measuring apparatus of the present invention solve the problem that the ozone concentration in the sample gas cannot be measured correctly when the light amount of the ultraviolet lamp varies, and even if the light amount of the ultraviolet lamp varies, The ozone concentration can always be measured correctly.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. In the present invention, while measuring the UV absorbance of the reference gas, as shown in FIG. 1, when the rate of change in UV absorbance of the reference gas, that is, the rate of change in the amount of light of the UV lamp exceeds a predetermined threshold value, By not calculating the ozone concentration in the sample gas from the ultraviolet absorbance of the sample gas and the reference gas, the abnormal measured value of the ozone concentration is cut.

In this case, the rate of change in the UV absorbance of the reference gas can be obtained from the following equation.
Change rate of UV absorbance of reference gas (%)
= [{R (n) -R (n-1)} / R (n-1)] * 100
R (n): UV absorbance of reference gas measured this time R (n-1): UV absorbance of reference gas measured last time

  The threshold value can be set as appropriate, but the absolute value of the threshold value of the change rate (%) of the UV absorbance of the reference gas described above is a predetermined value in the range of 0.01 to 1.0%, More preferably, it is appropriate to set a predetermined value in the range of 0.01 to 0.5%, more preferably a predetermined value in the range of 0.01 to 0.1%.

  Next, an example is shown. According to the simulation, the ozone concentration in the sample gas is not calculated when the rate of change in the UV absorbance of the reference gas exceeds a predetermined threshold, and the rate of change in the UV absorbance of the reference gas is The measurement result of the ozone concentration in the sample gas was examined when the ozone concentration in the sample gas was calculated when the value exceeded the limit. The results are shown in FIGS.

  FIG. 2 is a graph showing a change in lamp light quantity (light quantity of the ultraviolet lamp, the same applies hereinafter) a and a change rate b of the lamp light quantity (change ratio of the ultraviolet absorbance of the reference gas, the same applies hereinafter). FIG. 3 is a graph showing the change a of the lamp light amount with time a and the ozone concentration c in the sample gas when the ozone concentration is calculated when the change rate of the lamp light amount exceeds a predetermined threshold value. FIG. 4 is a graph showing a temporal change a of the lamp light amount and an ozone concentration d in the sample gas when the calculation for obtaining the ozone concentration is not performed when the change rate of the lamp light amount exceeds a predetermined threshold value. is there.

  From the comparison between FIG. 3 and FIG. 4, when the ozone concentration is calculated when the change rate of the lamp light amount exceeds a predetermined threshold (FIG. 3), the abnormal ozone concentration when the lamp light amount change is large. If the measured value appears and the ozone concentration cannot always be measured correctly, but the ozone concentration is not calculated when the rate of change in the lamp light intensity exceeds a predetermined threshold (FIG. 4), the lamp It can be seen that an abnormal ozone concentration measurement value does not appear even when the change in the amount of light is large, and therefore the ozone concentration in the sample gas can always be measured correctly. As described above, the effect of the present invention was confirmed by this experiment.

It is explanatory drawing which shows the concept of this invention. It is a graph which shows the time-dependent change of a lamp light quantity, and the change rate of a lamp light quantity. It is a graph which shows the time-dependent change of a lamp light quantity, and the measurement result of the ozone concentration in the sample gas by this invention. It is a graph which shows the time-dependent change of a lamp light quantity, and the measurement result of the ozone concentration in the sample gas by a conventional method. It is a block diagram which shows an example of the ozone measuring device by an ultraviolet absorption method.

Explanation of symbols

12 measurement cell 14 ultraviolet lamp 16 detector 18 comparison operation circuit

Claims (6)

  In the ozone measurement method for measuring the ultraviolet absorbance of the sample gas and the ultraviolet absorbance of the reference gas, and calculating the ozone concentration in the sample gas from these ultraviolet absorbances, the rate of change of the ultraviolet absorbance of the reference gas is a predetermined threshold value. And the ozone concentration in the sample gas is not calculated from the both ultraviolet absorbances. The ozone measurement method according to claim 1, wherein the change rate of the ultraviolet absorbance of the reference gas is calculated by the following formula.
Change rate of UV absorbance of reference gas (%)
= [{R (n) -R (n-1)} / R (n-1)] * 100
R (n): UV absorbance of reference gas measured this time R (n-1): UV absorbance of reference gas measured last time   The ozone measurement method according to claim 2, wherein an absolute value of a threshold value of a change rate (%) of the ultraviolet absorbance of the reference gas is set to a predetermined value in a range of 0.01 to 1.0%. .   In the ozone measuring apparatus that measures the ultraviolet absorbance of the sample gas and the ultraviolet absorbance of the reference gas, and calculates the ozone concentration in the sample gas from these ultraviolet absorbances, the change rate of the ultraviolet absorbance of the reference gas is a predetermined threshold value. And the ozone concentration in the sample gas is not calculated from the both ultraviolet absorbances. The ozone measuring device according to claim 4, wherein a rate of change in ultraviolet absorbance of the reference gas is calculated by the following formula.
Change rate of UV absorbance of reference gas (%)
= [{R (n) -R (n-1)} / R (n-1)] * 100
R (n): UV absorbance of reference gas measured this time R (n-1): UV absorbance of reference gas measured last time   6. The ozone measuring apparatus according to claim 5, wherein an absolute value of a threshold value of a change rate (%) of ultraviolet absorbance of the reference gas is set to a predetermined value in a range of 0.01 to 1.0%. .

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