JP2000162125A - Calibrating method and calibrating system of oxidant analyzer, and ozone generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a precise calibration by introducing an ozone gas having a concentration higher than a span calibrating gas to an analysis part by a span calibrating gas and then introducing the span calibrating gas to the analysis part to perform the calibration. SOLUTION: After it is instructed by an operation part 'to sent ozone gas of about 0.25 ppm after sending an aging gas', and an ozone gas having a concentration higher than a span calibrating gas, for example, several ppms, is generated to age a secondary reference ozone meter 3 and a measuring station oxidant analyzer 6. At this time, it is not desirable to set the concentration of the ozone gas to a high concentration of 10 ppm or more. An ozone gas of about 0.25 ppm is then generated and sent to both the secondary standard ozone meter 3 and the measuring station oxidant analyzer 6. The span of the measuring station oxidant analyzer 6 is regulated so that the instructing value of the measuring station oxidant analyzer 6 is conformed to the instructing value of the secondary standard ozone meter 3. After the span regulation, ozone gases of several concentrations may be sent to perform the linearity test of the measuring station oxidant analyzer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating an oxidant meter, a calibration system for an oxidant meter, and an ozone generator. More specifically, when calibrating an oxidant meter in the atmosphere, the aging of the oxidant meter is accurately performed. The present invention relates to a calibration method capable of performing and accurate calibration, an oxidant meter calibration system using the same, and an ozone generator that can be suitably used in the calibration method.

[0002]

2. Description of the Related Art Oxidants are a general term for oxidizing substances such as total oxidants, photochemical oxidants, and ozone. Oxidant meters for continuously measuring oxidants in the atmosphere include an automatic oxidant meter based on absorption spectroscopy, an automatic ozone meter based on chemiluminescence, and an automatic ozone meter based on ultraviolet absorption. Industrial standards have been established (JIS B 79
57-1992).

[0003] Like other atmospheric automatic measuring instruments, the oxidant automatic measuring instrument is used to prevent the occurrence of a measurement error due to clogging of a flow path, contamination of a measuring section, and mixing of dust into the measuring section.
A filter for removing dust contained in the air is provided near the sample air inlet. This filter is replaced periodically (usually about once every two weeks) in consideration of dust concentration and the like, and is also replaced when performing calibration.

[0004] However, it is known that when ozone gas passes through a new filter, the ozone gas concentration decreases. It is also known to reduce the concentration of ozone gas passing not only when a filter is replaced but also through a pipe in a new measuring device or a filter or a pipe after measuring a low-concentration ozone gas for a long time.

[0005] This phenomenon is gradually eliminated by passing a gas containing ozone in advance (aging). Therefore, a filter which has been aged in advance is used, or the span gas is measured until the indication becomes stable during span calibration. Aging filters and pipes had been used.

[0006]

However, if the above-mentioned aging is performed at an actual measurement site, there is a problem that it takes a long time and maintenance work is difficult, and the atmosphere cannot be measured during that time. Further, if span calibration is performed with insufficient aging in order to avoid missing measurements as much as possible, errors may occur in the calibration results, which may hinder accurate measurement.

In view of the above circumstances, the present invention provides a method of calibrating an oxidant meter that accurately performs aging of a filter or the like and enables accurate calibration, a calibration system of an oxidant meter using the same, and a method suitable for the calibration method. It is an object of the present invention to provide an ozone generator that can be used for an ozone generator.

[0008]

Means for Solving the Problems As a result of studying the above problems, the present inventor paid attention to the ease of decomposing ozone gas. In general, in measurement, when a low-concentration sample is measured after measuring a high-concentration sample, the influence of the high-concentration sample remains, and the measured value for a certain time tends to be higher for a certain period of time. However, with respect to easily decomposable ozone gas, it was confirmed that the residual effect was small even when the gas concentration was changed from a high concentration to a low concentration. Therefore, prior to the calibration, it was conceived that aging with high-concentration ozone gas was possible.

That is, in the method for calibrating an oxidant meter according to the first aspect, in the method for calibrating an oxidant meter for performing span calibration using ozone gas, after introducing an ozone gas having a higher concentration than the gas for span calibration into the analysis unit, A span gas is introduced by introducing a calibration gas into the analyzer.

Here, "higher concentration than the gas for span calibration" is not particularly limited as long as it is not less than a concentration at which a significant difference is observed in the aging effect compared with the concentration for the span calibration gas. If only low-concentration gas of 0.1 ppm (volume concentration, the same applies hereinafter) or less is used as the span calibration gas, the aging effect is improved even at about 0.2 ppm. High concentration ”.

"Higher concentration than gas for span calibration"
May be constant or may be changed on the way. For example, from a concentration around 10 times the gas concentration for span calibration,
The concentration may be gradually decreased to finally reduce the concentration to the span calibration gas concentration.

The introduction of the “span calibration gas” into the analysis unit is performed by using a “higher concentration ozone gas than the span calibration gas”.
May be performed continuously after completion of the introduction, or after some time has passed. However, introduction after too long time is not desirable because the aging effect is gradually lost.

According to the present calibration method, aging of the filters and pipes of the oxidant meter can be completed in a short time, so that accurate calibration can be performed while minimizing the missing time.

According to a second aspect of the present invention, there is provided an oxidant meter calibration system for performing span calibration using ozone gas, wherein after introducing an ozone gas having a higher concentration than the span calibration gas into the analysis unit, the span calibration is performed. A span gas is introduced by introducing a calibration gas into the analyzer.

As described above, the aging of the filter and the piping of the oxidant meter can be completed in a short time as described in the calibration system for the oxidant meter according to the first aspect of the present invention. In addition, it is possible to provide an oxidant meter calibration system capable of performing accurate calibration while performing the calibration.

The ozone generator according to claim 3 or 4 can be suitably used for the above-described method for calibrating the oxidant meter and the calibration system. That is, the ozone generator according to claim 3 is a concentration changing means for automatically changing the concentration of the span calibration gas to ozone gas after the ozone gas to be sent is made higher in concentration than the span calibration gas. It is characterized by having.

Here, “higher concentration than the gas for span calibration” means, as described above, the effect of aging.
There is no particular limitation as long as the concentration is not less than a concentration at which a significant difference is recognized as compared with the concentration of the span calibration gas. Further, the change from “higher concentration than span calibration gas” to “concentration of span calibration gas” may be gradually reduced, or may be reduced all at once or stepwise. In the course of the change, the ozone gas delivery may be interrupted for a certain period of time. The timing and speed of the change may be in accordance with the timing and speed set in advance, or the measurement value of the oxidant meter to which the data is sent may be fed back to perform control according to the progress of aging.

Further, the ozone generator according to claim 4 is
Ozone gas of 1 ppm or more can be delivered. As described above, ozone gas having a concentration of less than 1 ppm can be sent out as an aging gas as long as it is at or above a concentration at which a significant difference is observed in comparison with the concentration for the span calibration gas in the aging effect. However, in order to ensure the effect of aging, 1p
It is desirable to send out an ozone gas of pm or more as an aging gas.

The ozone generator according to the third or fourth aspect does not send out an aging gas, as in a normal ozone generator, and uses only one or two or more concentrations of the span calibration gas alone. Needless to say, it is desirable to also have a function of sending.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Since it is complicated to calibrate the oxidant meters of many measuring stations by comparing them with the manually analyzed values, the measuring stations use an ozone generator and a secondary standard as a practical method. Calibrate the oxidant meter in combination with a portable ozone meter.

FIG. 1 shows an embodiment of a calibration system for an oxidant meter according to the present invention, and shows a system for calibrating a secondary standard ozone meter with manual analysis values. In the present embodiment, the ozone gas generated by the ozone generator 1 is supplied to the secondary standard ozone meter 3 and the sample gas sampling device 4 via the manifold 2. The remaining ozone gas supplied to the secondary standard ozone meter 3 and the sample gas sampling device 4 overflows via the flow meter 5.

In the present embodiment, the principle of the ozone generator is not particularly limited, but a method using irradiation with a xenon flash lamp, a method using silent discharge, a method using irradiation with a mercury lamp, and the like can be adopted. In the method using the xenon flash lamp, the concentration of the ozone gas to be sent out with high linearity can be adjusted by adjusting the lighting frequency.
Also, the density can be adjusted by adjusting the voltage. In the silent discharge method, the concentration can be adjusted by adjusting the current. Further, in the method using irradiation with a mercury lamp, there is a method in which the density can be adjusted by adjusting the position of an irradiation amount adjusting sleeve that covers the irradiation surface in addition to adjusting the current.

FIG. 2 shows an embodiment of the ozone generator 1 in a case where a method based on irradiation of a xenon flash lamp is employed. In FIG. 2, the ozone generator 11
Zero gas is supplied through the filter 12 and the flow controller 13. Zero gas is gas used for zero calibration for adjusting the zero position of the oxidant meter, and purified air or the like from which air is purified to remove oxidants is used.

The ozone generator 11 is provided with a xenon flash lamp 14, which emits ozone by irradiating oxygen in gas passing therethrough with ultraviolet rays. The generated ozone gas is sent to the manifold via the mixer 15.

The xenon flash lamp 14 is powered by a power supply 16.
The lighting frequency is adjusted by the control device 17 connected to the power supply 16. An instruction is given to the control device 17 by the operation unit 18. The operation unit 18 selects whether the calibration gas is delivered after the aging gas is delivered, only the aging gas is delivered, or only the calibration gas is delivered. Can be set.

In FIG. 1, as the secondary standard ozone meter 3, an automatic ozone measuring device by an ultraviolet absorption method is usually used because it is easy to handle and easily portable. The sample gas sampling device is a device for subjecting the generated gas to manual analysis using an iodine standard solution. The flow meter 5 confirms that the ozone gas from the ozone generator 1 has a flow rate sufficient to supply the secondary standard ozone meter 3 and the sample gas sampling device, and overflows excess ozone gas. It is designed to be discharged outside. Note that an ozonizer for decomposing ozone gas is usually provided upstream or downstream of the flow meter 5.

When the calibration method according to the present invention is carried out using the system shown in FIG. 1 and the ozone generator shown in FIG. 2, for example, the following steps are performed. First, the operation unit 18 instructs that "ozone gas of about 0.4 ppm is to be sent out after the aging gas is sent out". As a step 1, secondary ozone gas having a higher concentration than the span calibration gas, for example, several ppm, is generated. The standard ozone meter 3 and the sample gas sampling device 4 are aged. At this time, as the concentration of the ozone gas is higher, the aging effect is increased and the process can be completed in a shorter time. However, it is not desirable to have a high concentration of, for example, 10 ppm or more. This is because not only does the filter and the piping deteriorate, but also the undecomposed ozone gas is discharged and pollutes the surrounding atmosphere. Step 1
May be terminated in a predetermined time, or may be terminated after confirming that the aging has been sufficiently performed when the indicated value of the secondary standard ozone meter 3 is stabilized. Next, as step 2, ozone gas of about 0.4 ppm is generated and sent to both the secondary standard ozone meter 3 and the sample gas sampling device 4. And the hand analysis value and the secondary standard ozone meter 3
Is determined in advance.

Next, “0.25 ppm
Send out the ozone gas before and after. In step 3, the relationship between the hand analysis value when ozone gas having a concentration of about 0.25 ppm is generated and the indication value of the secondary standard ozone meter 3 is obtained in advance.

Finally, “0.1 ppm” is
Send out the ozone gas before and after. In step 4, the relationship between the manually analyzed value when ozone gas having a concentration of about 0.1 ppm is generated and the indicated value of the secondary standard ozone meter 3 is obtained in advance.

The specific procedure from step 1 to step 4 follows a normal procedure, for example, the procedure of JISB7957. As a result of the experiment, it was confirmed that the indication of the secondary standard ozone meter 3 did not increase or became unstable due to the influence of the high-concentration aging gas. The procedure from step 1 to step 4 may be collectively instructed to the control device 17 as a collective instruction from the operation unit 18.

FIG. 3 shows another embodiment of a calibration system for an oxidant meter according to the present invention, and shows a system for calibrating with a secondary standard ozone meter on which a measuring station oxidant meter is graduated. In the present embodiment, the ozone gas generated by the ozone generator 1 is supplied to the secondary standard ozone meter 3 and the measuring station oxidant meter 6 via the manifold 2. The remaining ozone gas supplied to the secondary standard ozone meter 3 and the measuring station oxidant meter 6 overflows via the flow meter 5.

In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. The measuring station oxidant meter in FIG. 3 is not particularly limited to a measuring principle as long as it automatically measures the oxidant in the atmosphere, and may be a measuring instrument having the same principle as the secondary standard ozone meter. Usually, an automatic oxidant measuring device based on an absorption photometric method, an automatic ozone measuring device based on a chemiluminescent method, and an automatic ozone measuring device based on an ultraviolet absorption method are used.

When the calibration method according to the present invention is carried out using the system shown in FIG. 3 and the ozone generator shown in FIG. 2, for example, the following steps are performed as in the case of FIG. First, the operation section 18 instructs that "ozone gas of about 0.25 ppm is to be sent out after the aging gas is sent out". As a step 1, secondary ozone gas having a higher concentration, for example, several ppm than the span calibration gas is generated. The standard ozone meter 3 and the measuring station oxidant meter 6 are aged. At this time, immediately after the end of the operation in FIG. 1, the supply of the ozone gas to the secondary standard ozone meter 3 may be shut off, and the aging may be omitted. The ozone gas concentration at this time is shown in FIG.
As described with respect to this system, it is not desirable to use a high concentration of, for example, 10 ppm or more.

Next, as step 2, 0.25 pp
An ozone gas of about m is generated and sent to both the secondary standard ozone meter 3 and the measuring station oxidant meter 6. Then, the span of the measuring station oxidant meter 6 is adjusted so that the indicated value of the measuring station oxidant meter 6 matches the indicated value of the secondary standard ozone meter 3. After the span adjustment, ozone gas of several other concentrations may be sent out to perform the linearity test of the measuring station oxidant meter 6.

The specific procedure is a normal procedure, for example, JI
Follow the procedure of SB7957. As a result of the experiment, the measuring station oxidant meter 6
It was confirmed that there was no increase or instability of the instructions.

In the description of the system shown in FIGS. 1 and 3, the concentration of the ozone gas generated from the ozone generator 1 is set by controlling the lighting frequency by operating the operation section 18 of the ozone generator. However, it may be set based on a command signal from the secondary standard ozone meter 3, the measuring station oxidant meter 6, or an external arithmetic unit.

[0037]

According to the present invention, prior to calibration of the oxidant meter, aging of the oxidant meter can be completed accurately and in a short time. Therefore, it is possible to perform accurate calibration, and thus accurate measurement of the oxidant concentration, while minimizing the time of the missing state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a calibration system for an oxidant meter according to the present invention.

FIG. 2 is a configuration diagram showing one embodiment of an ozone generator according to the present invention.

FIG. 3 is a configuration diagram showing another embodiment of a calibration system for an oxidant meter according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ozone generator 2 Manifold 3 Secondary standard ozone meter 4 Sample gas sampling device 5 Flow meter 6 Measuring station oxidant meter 11 Ozone generator 12 Filter 13 Flow controller 14 Xenon flash lamp 15 Mixer 16 Power supply 17 Control device 18 Operation unit 21 Lighting frequency control signal

Claims (4)

[Claims] In an oxidant meter calibration method for performing span calibration using ozone gas, an ozone gas having a higher concentration than a span calibration gas is introduced into an analysis unit, and then the span calibration gas is introduced into the analysis unit. A method for calibrating an oxidant meter, comprising performing calibration. 2. In an oxidant meter calibration system for performing span calibration using ozone gas, after introducing ozone gas having a higher concentration than the span calibration gas into the analysis unit,
A calibration system for an oxidant meter, wherein a span calibration gas is introduced into an analyzer to perform span calibration. 3. An ozone generator for generating a gas for span calibration of an oxidant meter, wherein the ozone gas to be sent out has a higher concentration of ozone gas than the gas for span calibration.
An ozone generator having a concentration changing means for automatically changing the concentration of a span calibration gas to ozone gas. 4. An ozone generator for generating a gas for span calibration of an oxidant meter, wherein an ozone gas of 1 ppm or more can be delivered.