JP2006029968A - Instrument and method for measuring concentration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To directly measure a concentration of a measured substance in a medium, without requiring sampling and pretreatment for the medium containing the measured substance and a measuring error generating substance. <P>SOLUTION: A pulse light is emitted toward the medium comprising the measured substance and the measuring error generating substance to detect a received luminous energy of the pulse light transmitted through the medium and fluorescence luminous energy due to fluorescence of the measured substance generated by the irradiation of the pulse light, and the true concentration of the measured substance in the medium is obtained by setting off the first apparent concentration of the measured substance assumed with no measuring error generating substance contained in the medium, in which a received luminous energy value of the received pulse light is found pursuant to a correlation expression between the received luminous energy value and the concentration prepared in the medium under the condition the medium comprises only the measured substance and contains no measuring error generating substance, and the second apparent concentration of the measured substance assumed with no measuring error generating substance contained in the medium, in which the detected fluorescence luminous energy value is found pursuant to a correlation expression between the fluorescence luminous energy value and the concentration prepared in the medium under the condition the medium comprises only the measured substance and contains no measuring error generating substance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a concentration measurement technique for measuring the concentration of a substance to be measured in a medium containing the substance to be measured and a substance that generates a measurement error.

  In order to perform concentration control and property evaluation of substances such as NOx and SOx in exhaust gas from a boiler and the like, and nitrogen and phosphorus in wastewater from a wastewater treatment device, it is important to measure the concentration of the substance.

The following methods are known as conventional concentration measurement methods.
(1) Chemical analysis method A method in which a coloring reagent solution is colored with a medium containing a substance to be measured, and the concentration of the substance to be measured is measured by measuring the degree of coloration by the absorption light amount method.

(2) Automatic analysis method Chemiluminescence method: Measures the intensity of light emitted when a molecule to be measured excited by a chemical reaction returns from the excited state to the ground state, represented by a chemical reaction between NO and ozone (O3). To measure the concentration of the substance to be measured.

  Infrared absorption method: A method of measuring the concentration of a substance to be measured by measuring the absorbance of infrared light using the infrared absorption of the substance to be measured, represented by NO or NO2. In addition to the method based on the absorbance, a method of measuring the concentration of the substance to be measured by measuring the increase in pressure generated when the substance to be measured is heated and expanded by absorbing infrared rays.

Ultraviolet absorption method: A method of measuring the concentration of a substance to be measured by measuring the absorbance of the ultraviolet ray using the ultraviolet absorption of the substance to be measured, represented by NO or NO2.
Constant-potential electrolysis method: Applying a constant DC voltage to the electrode for electrolysis, using this as a detector, the electrolysis current when the measured substance in the medium containing the measured substance aerated in the electrolyte is electrolytically oxidized A method of taking out and measuring the concentration of the substance to be measured.

  In the above chemical analysis method, it takes time from collection of the medium containing the substance to be measured to completion of color development and concentration measurement, and each time the concentration measurement is performed, the process of collecting the medium containing the substance to be measured, completion of color development and concentration measurement is repeated. Therefore, there is a problem that continuous measurement is not suitable.

  All of the above-described automatic analysis methods are subject to interference by measurement error generating components such as smoke particles, CO 2, and water vapor, and thus have a problem of requiring preprocessing such as removal of these measurement error generating components. Furthermore, in order to guarantee a certain accuracy, it is necessary to keep the temperature and flow rate of the medium containing the substance to be measured and the measurement error generating component constant.

  Further, the conventional automatic analysis method has a problem that the concentration cannot be directly detected in the medium containing the substance to be measured. For this reason, since the medium containing the substance to be measured needs to be introduced to the concentration detection device by piping, tubes, etc., the time for the medium containing the substance to be measured to pass through this path is the measurement time from the collection of the medium to the concentration detection. There is a problem of delay.

In addition, a nitrogen oxide concentration measuring device using light absorption peculiar to the substance to be measured has been proposed (see Patent Document 1), but interference of components causing measurement error such as coexisting gas and smoke particles cannot be ignored. It is not clear whether true nitrogen oxide concentration can be measured with high accuracy.
JP-A-10-142147

  It is an object of the present invention to do not require sampling or pretreatment of a medium containing a substance to be measured and a measurement error generating component (measurement error generating substance), and to be measured in a boiler furnace, in a flue, in the air, in a water channel, etc. In addition, it is possible to directly measure the concentration of the substance to be measured in the medium containing the measurement error generating substance, and to measure the concentration of the substance to be measured in the medium containing the measurement substance and the measurement error generating substance in a very short time and continuously. An object of the present invention is to provide an apparatus and a method for measuring the concentration of a substance to be measured in a medium that can be measured in a simple manner.

The first invention of the present invention for solving the above-mentioned problems is
A concentration measuring device for measuring the concentration of a substance to be measured in a medium containing the substance to be measured and a substance that generates a measurement error,
A pulsed light source that irradiates the medium with pulsed light having an absorption light wavelength specific to the substance to be measured;
A light amount detecting means for detecting the light amount of the pulsed light that has passed through the medium and is attenuated by the absorption of the light of the substance to be measured and the measurement error generating substance;
A fluorescence light amount detecting means for detecting a fluorescence light amount that the substance to be measured fluoresces by irradiation with the pulsed light; and
Based on the received light quantity value detected by the above light quantity detection means, it is obtained from the correlation equation between the received light quantity value and the density created in advance in a medium in which the medium consists only of the substance to be measured and does not contain the measurement error generating substance. A first apparent concentration calculating means for calculating a first apparent concentration of a substance to be measured, assuming that the medium does not contain a measurement error generating substance;
Based on the correlation formula between the fluorescence light amount value and the concentration prepared in advance in the medium in which the medium is made of only the substance to be measured and does not include the measurement error generating substance based on the fluorescence light quantity value detected by the fluorescence light quantity detection means. A second apparent concentration calculating means for calculating a second apparent concentration of the substance to be measured, which is calculated on the assumption that the medium does not contain a measurement error generating substance;
The offset calculation is performed based on the apparent concentrations of the substance to be measured obtained by the first and second apparent concentration calculation means to cancel the measurement error due to the measurement error generating substance at the first and second apparent concentrations, and in the medium. The concentration measuring device comprises a concentration calculating means for calculating the true concentration of the substance to be measured.

The pulsed light source emits an absorption light wavelength specific to the substance to be measured.
The light amount detecting means irradiates a medium containing a measured substance and a measurement error generating substance with pulsed light, and is absorbed and attenuated by the measured substance and the measurement error generating substance after passing through the medium. Based on the detected light quantity, the first apparent density calculation means assumes that the medium is made of only the substance to be measured, and is prepared in a clean state that does not include a measurement error generating substance. The density is calculated as an apparent density from the correlation equation between the received light quantity value and the density.

  In addition, the fluorescence light quantity detection means detects the fluorescence light quantity that the substance to be measured fluoresces by the irradiation of the pulse light, that is, the light quantity of the fluorescence by the substance to be measured immediately after the light is shielded between the irradiation of the pulse light. The second apparent density calculation means detects and assumes that the medium is composed of only the substance to be measured based on the detected fluorescence light quantity, and the fluorescence light quantity value created in advance in a clean state that does not include the measurement error generating substance. The density is calculated as an apparent density from the correlation between the density and the density.

  In general, when a molecule is irradiated with light having a wavelength specific to the molecule, the light is absorbed by the molecule, and electrons in the molecule are excited from the ground state to the excited state. Since the amount of light absorbed at this time (absorption amount) is proportional to the number of molecules, the received light amount measured by the light amount detecting means can be used for concentration measurement (absorbed light amount method).

  On the other hand, when the light irradiated in the excited state is blocked, the electrons in the molecule fluoresce light having the same wavelength as the absorbed light when returning from the excited state to the ground state. At this time, the amount of fluorescent light (fluorescent light amount) is proportional to the number of molecules, so the fluorescent light amount measured by the fluorescent light amount detecting means can be used for concentration measurement (fluorescent light amount method).

When measuring the concentration of a substance to be measured in an actual medium, for example, when measuring the concentration of nitrogen oxides in a flue, an error occurs due to interference from coexisting substances such as CO, CO2, soot particles, and water vapor. For example, when measuring the concentration of nitrogen components in wastewater from wastewater treatment equipment, measurement errors occur due to interference from coexisting substances such as suspended substances contained in wastewater. Need to be corrected.
In the claims and specification of this application, such a coexisting substance that interferes with the concentration measurement of the substance to be measured is referred to as a measurement error generating substance.

  The error due to the coexisting substances (measurement error generating substances) works by apparently increasing the concentration of the substance to be measured in the absorbance method, and apparently lowering the concentration of the substance in the fluorescence method. By performing an offset calculation based on the concentration of the substance to be measured measured by the method and canceling the error, it is possible to measure the concentration of the true substance to be measured while correcting the error due to the coexisting substance (measurement error generating substance).

  Such cancellation calculation is performed by addition averaging. Note that the addition average is the concentration of a medium prepared by creating a calibration curve, which will be described later, and using the concentration measuring device to contain a measurement error generating substance in a medium (standard gas or standard solution) having a known substance concentration to be measured. It is desirable to measure in advance and obtain a denominator value to be used for addition averaging so that the measured concentration value becomes a known substance concentration to be measured.

The second invention of the present invention is:
A pulsed light quantity fluctuation detecting means for obtaining a light quantity fluctuation rate of the pulsed light source with respect to an initial emitted light quantity value of the emitted light quantity at the time of measurement of the pulsed light source, and detected by the light quantity detecting means based on the light quantity fluctuation rate of the pulsed light source 2. The concentration measuring apparatus according to claim 1, further comprising: a pulsed light amount fluctuation correcting unit that corrects the received light amount value of the pulsed light and the fluorescent light amount value detected by the fluorescence amount detecting unit.

  In general, the amount of light emitted from a light source changes from moment to moment, and the amount of emitted light decreases with age over the long term. The received light quantity value of the pulsed light detected by the light absorption of the substance to be measured and the measurement error generating substance and the fluorescence light quantity value detected by the fluorescence of the measured substance by the irradiation of the pulse light It is proportional to the amount of pulsed light. For example, if the light intensity of the pulsed light is large, the detected light intensity value and the fluorescent light intensity value are proportionally increased. If the light intensity of the pulse light is small, the detected light intensity value and the fluorescent light intensity value are proportionally small. Become.

  Therefore, in the present invention, by providing the pulsed light quantity fluctuation detecting unit and the pulsed light quantity fluctuation correcting unit, the received light quantity value and the fluorescent light quantity value of the detected pulsed light are proportional to the light quantity of the pulsed light that changes every moment. Thus, by always correcting, it is possible to convert the received light amount value and the fluorescent light amount value in the initial emitted light amount of the reference pulse light.

The third invention of the present invention is:
After using a correction light source having a wavelength different from the absorption light wavelength peculiar to the substance to be measured, superimposing the light of the correction light source on the pulse light, and passing through the optical path from the pulse light source to the light amount detection means Based on the light intensity value of the correction light source, the light attenuation rate at the time of measurement with respect to the initial value of the received light intensity due to the contamination of the optical path constituent member in the optical path is obtained, and the received light intensity value and the fluorescent light intensity value are respectively reduced. The density measuring apparatus according to claim 1, further comprising an optical path contamination correcting unit that performs correction based on the rate.

  Light dimming also occurs outside of the medium. In order to detect the attenuation of light other than the medium, light having a wavelength different from the absorption light wavelength specific to the substance to be measured, which is light having a wavelength at which light absorption by the substance in the medium does not occur in the medium, The light having an absorption light wavelength peculiar to the substance to be measured is passed through the same optical path, and the amount of light after passing is detected. In addition, the light attenuation other than the medium is a light attenuation due to the contamination of the optical path constituent member. For example, the optical path from the light source to the irradiation position of the light of the medium and the optical path constituent member from the light receiving position of the medium to the photodetector. This is dimming within the optical fiber or reduction in the reflectivity of the mirror due to objects accumulated in the mirror.

Such contamination of the optical path component causes an error in the measurement of the concentration of the substance to be measured by measuring the amount of received light and measuring the amount of fluorescent light.
In the present invention, in order to detect light loss due to optical path contamination, a correction light source having a wavelength different from the absorption light wavelength unique to the substance to be measured is used. Pass the same optical path, detect the amount of light after passing, find the light attenuation rate compared with the initial light source for correction, that is, the light amount after passing the optical path when creating the correlation equation, Light dimming correction due to optical path contamination is performed.

The fourth invention of the present invention is:
A pulsed light amount fluctuation detecting means for obtaining a light amount fluctuation rate of the pulsed light source with respect to an initial emitted light amount value of the emitted light amount at the time of measurement of the pulsed light source;
A pulsed light amount fluctuation correcting unit that corrects a received light amount value of the pulsed light detected by the light amount detecting unit and a fluorescent light amount value detected by the fluorescent amount detecting unit based on a light amount fluctuation rate of the pulsed light source;
A correction light source light quantity fluctuation detecting means for obtaining a light quantity fluctuation rate of the correction light source with respect to an initial light emission light quantity value of the light emission quantity at the time of measurement of the correction light source, and a light attenuation at the time of measurement based on the light quantity fluctuation rate of the correction light source 4. The density measuring apparatus according to claim 3, further comprising a correction light source light quantity fluctuation correcting means for correcting the rate.

  In the light source for correction, as in the case of the pulse light source, the amount of emitted light decreases with aging over the long term. In the present invention, the correction light source light quantity fluctuation detecting means and the correction light source light quantity fluctuation correcting means are provided, so that the light attenuation correction due to the optical path contamination for the detected received light quantity value and the fluorescent light quantity value is changed every moment. It is assumed that correct correction is performed by always correcting in proportion to the amount of light.

The fifth invention of the present invention is:
Irradiate the medium consisting of the substance to be measured and the substance causing the measurement error with pulsed light with a wavelength of absorption light unique to the substance to be measured. And the received light quantity value of the detected pulsed light was determined from the correlation equation between the received light quantity value and the concentration created with the medium consisting only of the substance to be measured and not including the measurement error generating substance, The first apparent concentration of the substance to be measured, which is assumed that the medium does not contain a measurement error generating substance, and the detected fluorescence light quantity value are created on a medium in which the medium consists only of the substance to be measured and does not contain the measurement error generating substance. The first and second apparent values are calculated by performing an offset operation based on the second apparent concentration of the substance to be measured, which is calculated from the correlation equation between the measured fluorescence light quantity value and the concentration, and that the medium does not contain the measurement error generating substance. In concentration Remove measurement errors producing the measuring error due to measurement error generating material from the measurement error generating substance in the medium to offset the concentration measurement method of the measured substance.

  According to the present invention, the concentration of the substance to be measured in the medium containing the measurement error generating substance can be set to interfere with the measurement of the substance to be measured of the measurement error generating substance in the medium only by setting the optical path in the medium. Eliminates and can measure easily and accurately without measuring time delay.

  In the present invention, in a space where a substance to be measured is supposed to exist, when the installation position of the reflecting mirror is separated from the light irradiation location and the optical path in the medium is made long, the average concentration in the space is calculated. Can be measured. On the other hand, when the installation position of the reflecting mirror is set to a very short distance from the light irradiation location, the concentration is measured in this very short distance space and can be measured as the concentration at the pinpoint location.

FIG. 1 shows the overall configuration of the present invention.
The medium 200 is a gas or a liquid containing a substance to be measured whose concentration is to be measured. As described above, this medium contains a component (measurement error generating substance) that interferes with the concentration measurement. In the present invention, the concentration measurement can be performed without the influence of the component.

  The substance to be measured has an absorption light wavelength peculiar to the substance, and the pulse light source 100 irradiates the medium 200 with pulsed light having an absorption light wavelength peculiar to such a substance to be measured. The light quantity detection means 300 receives the pulsed light that has been attenuated by passing through the medium 200 and detects the received light quantity. The fluorescence light amount detection means 350 detects the fluorescence light amount that the substance to be measured fluoresces by the pulsed light irradiation.

  Based on the value of the received light quantity, the first apparent density calculation means 400 is configured to obtain the received light quantity value and the density obtained in advance as a medium in which the medium is composed of only the substance to be measured and does not include the measurement error generating substance. From this correlation formula, the received light quantity value is calculated as the density when the medium is assumed to be composed of only the substance to be measured, that is, the first apparent density.

  The second apparent density calculation means 450 is based on the detected fluorescence light quantity value, and the fluorescence light quantity value and density obtained in advance as a medium in which the medium is made of only the substance to be measured and does not contain the measurement error generating substance. From this correlation equation, the concentration of this fluorescence light amount value when the medium is assumed to be composed only of the substance to be measured, that is, the second apparent concentration is calculated.

  As described above, the concentration calculation means 500 calculates a higher concentration by the measurement error generating substance at the first apparent concentration, and calculates a lower concentration by the measurement error generating substance at the second apparent concentration. Therefore, based on the both, the influence of the measurement error generating substance can be offset and the concentration of the true measured substance in the medium 200 can be calculated.

  Members constituting the optical path, such as optical fibers and mirrors, are fouled by aging and cause errors in density measurement. In the present invention, an optical path contamination correcting means 800 for detecting the degree of contamination of the optical path to calculate the light attenuation rate and correcting the received light amount value and the fluorescent light amount value based on the degree of contamination (light attenuation rate) is appropriately provided.

The optical path contamination correcting means 800 uses a correction light source 600 having a wavelength different from the absorption light wavelength peculiar to the substance to be measured, superimposes the light of the correction light source 600 on the pulsed light, and from the pulse light source 100 to the above Based on the light quantity value of the light from the correction light source 600 that has passed through the optical path leading to the light quantity detection means, the light reduction rate at the time of measurement with respect to the initial value of the received light quantity accompanying the contamination of the optical path constituent member in the optical path is obtained, The fluorescent light quantity values are respectively corrected based on the dimming rate.
Here, the optical path contamination correcting unit 800 includes a light amount detection unit and a light reduction rate calculation unit, which will be described later.

  Further, in the pulsed light source 100 that emits light having an absorption light wavelength peculiar to the substance to be measured and the correction light source 600 having another wavelength that is superimposed on this light, the amount of emitted light varies every moment. In order to eliminate the measurement error due to this variation, it is necessary to correct the measurement result of the received light amount or the fluorescent light amount in accordance with the varying light amount.

  The light quantity fluctuation of the light source of the pulsed light is detected by the light quantity detection means 300 and the fluorescence light quantity detection means 350 provided as necessary with a means 900 for detecting the light emission quantity fluctuation of the pulse light source 100 and a light emission quantity fluctuation correction means 950. The values of the received light quantity and the fluorescent light quantity are corrected so that there is no error due to fluctuations in the emitted light quantity.

  As for the light amount fluctuation of the correction light source 600, a correction light source light quantity fluctuation detection means 700 and a correction light source light quantity fluctuation correction means 750 are provided as necessary. The fluctuation is corrected to correct the optical path contamination correction, and the values of the received light amount and the fluorescent light amount detected by the light amount detecting means 300 and the fluorescent light amount detecting means 350 are corrected so that there is no error due to the optical path contamination.

  In general, the correlation equation is obtained from the light intensity measurement result by using a standard gas or a standard solution of various concentrations known for both the light absorption light intensity method and the fluorescence light intensity method in the concentration measuring device. From this result, a correlation equation (calibration curve) between the concentration and the received light amount value or the fluorescent light amount value is obtained. At the time of density measurement, an apparent density is obtained from a comparison between the measured received light quantity value or fluorescent light quantity value and the correlation equation.

Embodiments of the present invention will be described in detail below with reference to the drawings, mainly for measuring the concentration of gas in a flue.
FIG. 2 is a schematic diagram showing the equipment configuration of the measurement substance concentration measuring apparatus according to the present invention.

The device configuration will be described.
The measurement light source 2 is a light source that emits light having an absorption light wavelength unique to the substance to be measured. For example, if the substance to be measured is a concentration measurement of nitrogen oxides in a flue, it is desirable to emit light in the near infrared region having a wavelength of 1.28 to 1.86 μm. This light is laser light that has a constant frequency, is in phase, does not spread light, and can be irradiated with a very thin optical axis.

  A fixed mirror 6 is disposed on the optical path of light from the measurement light source 2. The fixed mirror 6 is a half-passing half mirror, and the light is divided into two. One of the divided lights is incident on a light quantity fluctuation correcting photodetector 4 that measures the light emission quantity of the light source 2. The other light is irradiated from the fixed mirror 6 to the medium 200 for measuring the concentration of the substance to be measured, and an optical pulse generator 14, a light synthesizer 7, and a fixed mirror 12 are disposed on the optical path.

  The light irradiated on the medium 200 is reflected by the fixed mirror 12. An optical separator 9 and a fixed mirror 15 are disposed on the optical path of the reflected light. The fixed mirror 15 is a half-passing half mirror, and the light is divided into two. An optical pulse generator 14 is disposed on the optical path of the divided light. One of the halved lights passes through the slit of the optical pulse generator 14 and is incident on the measurement photodetector 16 which is a light amount detection means 300 that detects the light amount. The other light is obstructed between the slits of the optical pulse generator 14 and cannot pass through the optical pulse generator 14, but the measurement fluorescence detector 10 which is a fluorescence light amount detection means 350 is disposed on the extension of the optical path. . The light combiner 7 and the light separator 9 may be the same prism.

  In the present invention, the correction light source light quantity fluctuation correcting means 750, the light attenuation rate calculating part of the optical path contamination correcting means 800, the pulsed light quantity fluctuation correcting means 950, the first apparent density calculating means 400, the second apparent density calculating means 450, and The density calculation means 500 can be realized by the arithmetic unit 13 that operates by a predetermined program stored in a ROM (not shown), that is, a processing device (CPU). Each of the above means can be constituted by hardware using electronic components for each means instead of such software.

  Signals detected by the light quantity fluctuation correcting photodetector 4, the measurement fluorescence detector 10, and the measurement photodetector 16, which are the pulsed light quantity fluctuation detecting means 900, are input to the calculator 13. The photodetector is, for example, an optical semiconductor that can quantitatively detect the amount of light.

  The correction light source 1 (correction light source 600) is a light source of light having a different wavelength that is superimposed on light having an absorption light wavelength unique to the substance to be measured of the measurement light source 2. A fixed mirror 5 is disposed on the optical path of the light from the correction light source 1. The fixed mirror 5 is a half-passing half mirror, and the light is divided into two. One of the divided lights is incident on a first optical path contamination correction photodetector 3 that measures the amount of light emitted from the light source 1. The other light is emitted from the fixed mirror 5 to the medium. A light combiner 7 is disposed on the optical path, and is superimposed on the light having the absorption light wavelength peculiar to the substance to be measured.

The irradiated light is reflected by the fixed mirror 12. An optical separator 9 is disposed on the optical path of the reflected light, and the light enters the optical path contamination correction second photodetector 11 that measures the amount of received light. The light combiner 7 and the light separator 9 may be the same prism.
Signals detected by the optical path contamination correction first photodetector 3 and the optical path contamination correction second photodetector 11 which are light quantity detection units in the optical path contamination correction means 800 are input to the calculator 13.

  The light emitted from the correction light source 1 and the measurement light source 2 is laser light that has a narrow spectrum width, constant frequency, uniform phase, does not spread light, and can irradiate a very thin optical axis. The mirror fixing device 8 is a tube having a hollow inside so as not to disturb the optical path. A light emitting unit 21 and a light receiving unit 22 are installed at one end, and a fixed mirror 12 is installed at the other end.

  The mirror fixing device 8 is fixedly installed at a detection seat which serves to fix the mirror fixing device 8 by making a hole in a flow path structure of the medium 200, for example, a flue, and is inserted into the flow channel. As a result, the fixed mirror 15 is fixed without losing the medium flow. The light emitting unit 21 is a part that irradiates the light to the medium 200, and the light receiving part 22 is a part that receives the light from the medium 200. The light emitting unit 21 and the light receiving unit 22 are windows opened in a detection seat provided in the flue, and when the optical fiber 20 transmits and receives light to and from the concentration measuring device main body, the light emission of the optical fiber 20 is performed. End or light receiving end is connected.

  In the above case, the light is reflected by using the fixed mirror 15 in order to make the light transmission / reception to the medium 200 the same direction. However, the light transmission / reception is performed opposite to each other. You may install the light emission part 21 and the light-receiving part 22 in the position where a path | route opposes.

  The optical pulse generator 14 is a rotating disk provided with slits having the same gap width at equal intervals shown in FIG. The light from the measurement light source 2 is reflected by the fixed mirror 6 and irradiated into the medium through the slit at the measurement light irradiation position 17. In this way, the light from the measurement light source 2 becomes pulsed light and is irradiated onto the medium by the rotation of the disk having the slits. The measurement light source 2 and the optical pulse generator 14 constitute the pulse light source 100 of the present invention.

  The reflected light from the fixed mirror 12 is reflected by the fixed mirror 15 to the received light amount measuring position 19 toward the measuring light detector 16 and to the fluorescent light amount measuring position 18 toward the measuring fluorescence detector 10. Divided by 2 along the optical axis.

  FIG. 4 shows the positional relationship of the slits of the measurement light irradiation position 17, the received light quantity measurement position 19, and the fluorescent light quantity measurement position 18 of the measurement light source 2. While the slit at the measurement light irradiation position 17 is opened and the light is irradiated into the medium through the slit, the slit at the received light quantity measurement position 19 is opened, while at the fluorescence light quantity measurement position 18, the slit is closed. Become shielded from light. The slit at the measurement light irradiation position 17 is closed and shielded, and at the same time the received light quantity measurement position 19 is also closed, but at the fluorescent light quantity measurement position 18, the slit is opened.

  With respect to the width of the slit, the interval between the slits, and the rotational speed of the disk, a sufficient time for measuring the amount of received light that is considerably longer than the 90% response time constant of the measuring photodetector 16 and 90% of the measuring fluorescence detector 10 are obtained. The time is set so that a sufficient time can be secured for the measurement of the amount of fluorescent light, which is considerably longer than the response time constant.

The operation of each device will be described.
Light emitted from the measurement light source 2 which is a light source of light having an absorption light wavelength peculiar to the substance to be measured is divided into two by a half mirror fixed mirror 6. The amount of light passing through the fixed mirror 6, which is one of the halved lights, is measured by the light amount fluctuation correcting photodetector 4. The measured light quantity is used to measure the fluctuation of the emitted light quantity of the measurement light source 2. The reflected light of the fixed mirror 6, which is the other light divided into two, passes through the optical pulse generator 14, is processed into pulsed light, and is converted into a substance to be measured emitted from the correction light source 1 by the light combiner 7. Superposed on light having a wavelength different from that of light having a specific absorption light wavelength.

  The light emitted from the correction light source 1 that is a light source of light of another wavelength superimposed on the light of the absorption light wavelength peculiar to the substance to be measured is divided into two by the half mirror fixed mirror 5. The amount of light passing through the fixed mirror 5, which is one of the two divided lights, is measured by the first optical path contamination correction first photodetector 3. The measured light amount is used to measure the light emission amount fluctuation of the correction light source 1. The reflected light of the fixed mirror 5, which is the other divided light, is superimposed on the light having the absorption light wavelength specific to the substance to be measured emitted from the measurement light source 2 by the light combiner 7.

  The light of the absorption light wavelength peculiar to the substance to be measured and the light of a different wavelength (correction light) superimposed by the light combiner 7 pass through the cavity in the mirror fixing device 8 and are reflected by the fixed mirror 12. Is done. The distance between the mirror fixing device 8 outlet and the fixed mirror 12 has a known fixed length, and light having an absorption light wavelength peculiar to the substance to be measured is absorbed or fluorescent by the substance to be measured existing therebetween.

  Light reflected by the fixed mirror 12 or light fluorescent between the fixed mirror 12 and the exit of the mirror fixing device 8 passes through a cavity in the tube of the mirror fixing device 8 and is absorbed by the light separator 9 and is specific to the substance to be measured. The light is separated into light for wavelength measurement and light for optical path contamination correction on which light of a different wavelength is superimposed.

  The light having the absorption light wavelength peculiar to the substance to be measured separated by the light separator 9 is divided into two by the half mirror fixed mirror 15. One of the divided lights passes through the optical pulse generator 14 and is incident on the measurement fluorescence detector 10. The amount of light measured by the measurement fluorescence detector 10 is the amount of light that is fluorescent by the substance to be measured that exists between the exit of the mirror fixing device 8 and the fixed mirror 12. The other light passes through the optical pulse generator 14 and enters the measurement photodetector 16. The amount of light measured by the measurement light detector 16 is detected by the light emitted from the measurement light source 2 being absorbed and reduced by the substance to be measured present between the exit of the mirror fixing device 8 and the fixed mirror 12. The amount of light that reaches the device 16.

  The correction light having another wavelength superimposed on the light having the absorption light wavelength peculiar to the substance to be measured separated by the light separator 9 is incident on the second optical detector 11 for correcting optical path contamination. The amount of light measured by the second optical detector 11 for correcting optical path contamination is reduced due to optical path contamination such as the light emitted from the correcting light source 1 being in the optical path of an optical fiber or the like, or the reflectance of the fixed mirror 12 being reduced. The amount of light reaching the second optical detector 11 for correcting optical path contamination.

The calculation from the measured light amount to the density will be described with reference to FIG.
Correlation equations used in the first apparent density calculation unit 400 and the second apparent density calculation unit 450 are obtained as follows.
Measurement is performed only with standard gases or standard solutions having various known concentrations. At this time, the correlation formula (calibration curve) between the fluorescence light quantity value and the concentration measured by the measurement fluorescence detector 10 and the measurement photodetector 16 are used. A correlation equation (calibration curve) between the measured received light quantity value and concentration is prepared in advance.

  At the time of creating the calibration curve, an initial light emission quantity value used as a reference for correction of emission light quantity fluctuation of the measurement light source 2 is also measured by the light quantity fluctuation correction photodetector 4 in the pulse light quantity fluctuation correction means 950. deep.

  In addition, when the calibration curve is created, the initial light emission amount value used as a reference for correction of the light emission amount variation of the correction light source 1 is used in the correction light source light amount variation correction means 750 in the optical path contamination correction first photodetector 3. A and the second optical detector 11 for correcting optical path contamination, there is no particle such as smoke particles used for calculating the attenuation rate in the attenuation rate calculation unit of the optical path contamination correcting means 800, and the fixed mirror 12 is clean. For example, an initial received light amount value B of the correction light source 1 which is a reference for correction of received light amount fluctuation due to optical path contamination in a state where the optical path is not contaminated is measured.

  The amount of light received from the measurement light source 2 at the time of measuring the concentration of the substance to be measured in the medium containing the substance to be measured and the substance having the measurement error is measured by the light quantity fluctuation correcting photodetector 4. The received light quantity value is divided by the initial emitted light quantity value C of the measurement light source 2 to obtain the emission light quantity fluctuation correction coefficient a of the measurement light source 2 (pulse light quantity fluctuation correction means 950).

  The first light detector 3 for correcting optical path contamination measures the amount of light received from the correction light source 1 when measuring the concentration of the measurement substance in the medium containing the measurement substance and the measurement error generating substance (correction light source light quantity fluctuation detecting means). 700). The received light quantity value is divided by the initial emission light quantity value A of the correction light source 1 to obtain the emission light quantity fluctuation correction coefficient b of the correction light source 1 (correction light source quantity fluctuation correction means 750).

  The second light detector 11 for correcting optical path contamination measures the amount of light received from the correction light source 1 when measuring the concentration of the substance to be measured in the medium containing the substance to be measured and the substance having the measurement error. This light reception state is a state in which the optical path is contaminated, such as dimming in the optical path such as an optical fiber, and a decrease in the reflectance of the fixed mirror 12.

  After correcting the influence of the received light quantity value of the correction light source 1 on the received light quantity value by dividing the received light quantity value of the second optical detector 11 for correcting optical path contamination by the emission light quantity fluctuation correction coefficient b of the correction light source 1, The corrected received light amount value is divided by the initial received light amount value B when there is no optical path contamination at the time of creating the calibration curve by the optical path contamination correction second photodetector 11, so that it can be obtained in the optical path of an optical fiber or the like. A light quantity fluctuation correction coefficient due to optical path contamination, that is, a light reduction rate is obtained to correct fluctuations in received light quantity due to light reduction and fluctuations in received light quantity due to optical path contamination of the fixed mirror 12 (optical path contamination correction means 800).

  Here, the light quantity fluctuation correction coefficient (dimming rate) due to the optical path contamination represents what percentage of the light quantity incident on the optical path the light quantity after passing through the optical path due to the optical path contamination at the time of density measurement. .

  The light quantity of light received from the measurement light source 2 after being absorbed by the substance to be measured measured by the measurement light detector 16 is obtained from the light quantity of light for measurement 2 created from the light quantity of light received by the light quantity fluctuation correcting photodetector 4. Dividing the emission light quantity fluctuation correction coefficient a to correct the emission light quantity fluctuation of the measurement light source 2 (light emission quantity fluctuation correction, pulsed light quantity fluctuation correction means 950).

Thereafter, the received light quantity value of the measurement photodetector 16 is corrected by dividing by the light quantity fluctuation correction coefficient (dimming rate) due to the optical path dirt created from the received light quantity value of the second optical path detector 11 for correcting optical path pollution ( Optical path contamination correction, optical path contamination correction means 800).
By making these corrections, the measurement conditions can be made the same as when creating the calibration curve, so by substituting the corrected received light quantity value into the correlation equation between the received light quantity value and the density, a measurement error occurs from the received light quantity. An apparent measured substance concentration including an error due to the substance is obtained (first apparent concentration calculating means 400).

  Measured by dividing the fluorescence light quantity value measured by the measurement fluorescence detector 10 with the light emission quantity fluctuation correction coefficient a of the measurement light source 2 created from the received light quantity value of the light quantity fluctuation correction photodetector 4. The light emission fluctuation of the light source 2 is corrected (light emission fluctuation correction, pulsed light quantity fluctuation correction means 950).

Thereafter, the fluorescence light quantity value of the measurement fluorescence detector 10 is corrected by dividing by the light quantity fluctuation correction coefficient (dimming rate) due to the optical path dirt created from the received light quantity value of the second optical path detector 11 for optical path dirt correction ( Optical path contamination correction, optical path contamination correction means 800).
By making these corrections, the measurement conditions can be made the same as when creating the calibration curve, so by substituting the corrected fluorescent light quantity value into the fluorescent light quantity / concentration correlation equation, the fluorescent light quantity can be determined from the measurement error generating substance. An apparent measured substance concentration including an error is obtained (second apparent concentration calculation means 450).

  In the concentration calculation means 500, an apparent measured substance concentration (first apparent density) including an error due to a measurement error generating substance obtained from the received light quantity and an error due to a measurement error generating substance obtained from the fluorescent light quantity are included. With the apparent measured substance concentration (second apparent concentration), the error due to the measurement error generating substance becomes higher and lower, respectively. Can do.

  As mentioned above, the case where the substance to be measured is a gas in the flue has been mainly described. However, the measurement method of the present invention is the same when the substance to be measured is a substance (phosphorus, nitrogen, etc.) contained in the waste water. Applicable in equipment configurations of

It is a schematic diagram which shows the whole structure of the to-be-measured substance concentration measuring apparatus concerning this invention. It is a schematic diagram which shows the apparatus structure of the to-be-measured substance concentration measuring apparatus concerning this invention. It is a schematic diagram which shows the shape and apparatus structure concerning an optical pulse generator. It is a schematic diagram which shows the timing of the light pulse in the generator of FIG. 3, light reception light quantity measurement, and fluorescence light quantity measurement. It is a calculation schematic diagram related to the measurement substance concentration calculation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Correction light source 2 Measurement light source 3 Optical path contamination correction 1st photodetector 4 Light quantity fluctuation correction photodetectors 5, 6, 12, 15 Fixed mirror 7 Photosynthesis device 8 Mirror fixing device 9 Optical separator 10 Measurement fluorescence Detector 11 Second optical detector 13 for correcting optical path contamination 13 Operation unit 14 Optical pulse generator 16 Measuring photodetector 17 Measuring light irradiation position 18 Fluorescent light amount measuring position 19 Received light amount measuring position 100 Pulse light source (Concentration measuring light) )
200 Medium 300 Light quantity detection means 350 Fluorescence light quantity detection means 400 First apparent density calculation means 450 Second apparent density calculation means 500 Concentration calculation means 600 Correction light source 700 Correction light source light quantity fluctuation detection means 750 Correction light source light quantity fluctuation correction Means 800 Optical path contamination correction means 900 Pulsed light quantity fluctuation detecting means 950 Pulsed light quantity fluctuation correcting means

Claims (5)

A concentration measuring device for measuring the concentration of a substance to be measured in a medium containing the substance to be measured and a substance that generates a measurement error,
A pulsed light source that irradiates the medium with pulsed light having an absorption light wavelength specific to the substance to be measured;
A light amount detecting means for detecting the light amount of the pulsed light that has passed through the medium and is attenuated by the absorption of the light of the substance to be measured and the measurement error generating substance;
A fluorescence light amount detecting means for detecting a fluorescence light amount that the substance to be measured fluoresces by irradiation with the pulsed light; and
Based on the received light quantity value detected by the above light quantity detection means, it is obtained from the correlation formula between the received light quantity value and the density created in advance in a medium in which the medium consists only of the substance to be measured and does not contain the measurement error generating substance. A first apparent concentration calculating means for calculating a first apparent concentration of a substance to be measured, assuming that the medium does not contain a measurement error generating substance;
Based on the correlation formula between the fluorescence light quantity value and the concentration prepared in advance in a medium in which the medium is made of only the substance to be measured and does not contain the measurement error generating substance based on the fluorescence light quantity value detected by the fluorescence light quantity detection means. A second apparent concentration calculating means for calculating a second apparent concentration of the substance to be measured, on the assumption that the medium does not contain a measurement error generating substance;
The offset calculation is performed based on the apparent concentrations of the substance to be measured obtained by the first and second apparent concentration calculation means to cancel the measurement error due to the measurement error generating substance at the first and second apparent concentrations, and in the medium. A concentration measuring device comprising: concentration calculating means for calculating the true concentration of the substance to be measured. A pulsed light quantity fluctuation detecting means for obtaining a light quantity fluctuation rate of the pulsed light source with respect to an initial emitted light quantity value of the emitted light quantity at the time of measurement of the pulsed light source, and detected by the light quantity detecting means based on the light quantity fluctuation rate of the pulsed light source 2. The concentration measuring apparatus according to claim 1, further comprising: a pulsed light amount fluctuation correcting unit that corrects the received light amount value of the pulsed light and the fluorescent light amount value detected by the fluorescent amount detecting unit. After using a correction light source having a wavelength different from the absorption light wavelength peculiar to the substance to be measured, superimposing the light of the correction light source on the pulse light, and passing through the optical path from the pulse light source to the light amount detection means Based on the light intensity value of the correction light source, the light attenuation rate at the time of measurement with respect to the initial value of the received light intensity due to the contamination of the optical path constituent member in the optical path is obtained, and the received light intensity value and the fluorescent light intensity value are respectively reduced. The density measuring apparatus according to claim 1, further comprising optical path contamination correcting means for correcting based on the rate. A pulsed light amount fluctuation detecting means for obtaining a light amount fluctuation rate of the pulsed light source with respect to an initial emitted light amount value of the emitted light amount at the time of measurement of the pulsed light source;
A pulsed light amount fluctuation correcting unit that corrects a received light amount value of the pulsed light detected by the light amount detecting unit and a fluorescent light amount value detected by the fluorescent amount detecting unit based on a light amount fluctuation rate of the pulsed light source;
A correction light source light quantity fluctuation detecting means for obtaining a light quantity fluctuation rate of the correction light source with respect to an initial light emission light quantity value of the light emission quantity at the time of measurement of the correction light source, and a light attenuation at the time of measurement based on the light quantity fluctuation rate of the correction light source The density measuring apparatus according to claim 3, further comprising a correction light source light quantity fluctuation correcting unit that corrects the rate. Irradiate the medium consisting of the substance to be measured and the substance causing the measurement error with pulsed light with a wavelength of absorption light unique to the substance to be measured. And the received light quantity value of the detected pulsed light was determined from the correlation equation between the received light quantity value and the concentration created with the medium consisting only of the substance to be measured and not including the measurement error generating substance, The first apparent concentration of the substance to be measured, which is assumed that the medium does not contain a measurement error generating substance, and the detected fluorescence light quantity value are created on a medium in which the medium consists only of the substance to be measured and does not contain the measurement error generating substance. The first and second apparent values are calculated by performing an offset operation based on the second apparent concentration of the substance to be measured, which is calculated from the correlation equation between the measured fluorescence light quantity value and the concentration, and that the medium does not contain the measurement error generating substance. In concentration A method for measuring the concentration of measurement error generating material measured substance removing measurement errors emanating from the measurement error generating substance in the medium by canceling a measurement error due to

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