JP2015227828A - Laser type oxygen analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser type oxygen gas analyzer which measures a gas concentration of an oxygen gas having a wide range of temperatures using a plurality of wavelengths different in absorption intensity for a gas temperature.SOLUTION: A laser type oxygen analyzer emits a laser beam large in absorption intensity of an oxygen gas of a high temperature and small in absorption intensity of a normal temperature oxygen gas, and a laser beam of a wavelength for a normal temperature measurement large in absorption intensity of the high temperature oxygen gas which is the wavelength adjacent to the wavelength for the high temperature measurement, and the gas intensity of the high temperature oxygen gas is measured by using the detection light for the high temperature measurement, and a gas concentration of the normal temperature oxygen gas is measured by using the detection light for the normal temperature measurement.

Description

  The present invention relates to a laser-type oxygen gas analyzer that measures the gas concentration of oxygen gas from a low temperature to a high temperature with high accuracy using a difference in absorption intensity between gas temperatures of two wavelengths.

It is known that each gas molecule in gas has its own light absorption spectrum. For example, FIG. 23 is an example of a light absorption spectrum of oxygen gas (O ₂ gas), where the horizontal axis indicates the wavelength and the vertical axis indicates the absorption intensity. The greater the absorption intensity on the vertical axis, the greater the amount of light absorption. The laser-type oxygen gas analyzer is equipped with a laser element that emits laser light of a wavelength that is absorbed by the target oxygen gas, and detects the presence or absence of oxygen gas by absorbing the laser light of this specific wavelength into the oxygen gas. can do. In addition, the laser oxygen gas analyzer can detect the concentration because the absorption intensity of the laser light at a specific wavelength is proportional to the concentration of oxygen gas.

  Such a laser-type oxygen gas analyzer is particularly used for atmospheric environment measurement and control purposes, and specifically, is often used mainly for combustion control in a garbage incineration plant or the like. Generally, the temperature of the measurement target gas which is a target of a laser oxygen gas analyzer used for combustion control is as high as 700 to 1200 ° C. In addition, dust may be included. Therefore, purging with gas (hereinafter referred to as purge gas) must be performed at all times in order to protect the device from heat, prevent piping blockage, and prevent dust from sticking to windows.

  FIG. 24 shows the external structure when a laser-type oxygen gas analyzer is installed at a measurement location such as a boiler, and the flow of flue gas and purge gas to be measured. In the wall 40, flue gas generated by combustion flows. Further, purge gas is introduced from the purge gas inlets 20 and 60, and the purge gas prevents contamination of the lens and glass window on the surface of the light emitting unit box 10 and the light receiving unit box 70. The purge gas is discharged into the wall 40 through the companion flanges 30 and 50.

  The purge gas includes instrument air and instrument nitrogen. When the purge gas is instrument air, the instrument air contains oxygen, and the analysis of the flue oxygen gas is affected by the oxygen gas in the instrument air. In addition, when the purge gas is instrumentation nitrogen, it does not affect the gas concentration of the oxygen gas that is the object of measurement, but the use of instrumentation nitrogen requires equipment and operational costs, so it is mainly a fire called steelworks.・ It is only used in places where there is a risk of explosion. After all, most common incinerators use instrument air.

  The instrument air described above usually contains about 20.6 vol% oxygen. The laser oxygen gas analyzer is affected by the oxygen of about 20.6 vol% when measuring air is used as the purge gas. In order to avoid this influence, a method is conceivable in which the oxygen amount of the oxygen gas contained in the instrument air is obtained and the concentration is converted in advance as an offset and then measured. However, the oxygen amount of oxygen gas generally used for combustion control in the boiler is several vol% (for example, 3 to 7 vol%), and the gas concentration of oxygen gas contained in instrument air is relatively higher. Increases and affects measurement accuracy. In the worst case, high temperature gas may not provide sufficient S / N. For this reason, the oxygen meter used for combustion control is not a laser-type oxygen gas analyzer, but another type of oxygen meter (zirconia oxygen meter) has been used. There was also a problem that they had to be replaced annually.

  Therefore, by using the temperature difference between the purge gas and the oxygen gas contained in the atmosphere and the oxygen gas contained in the measurement target gas, it is possible to show almost sensitivity to the purge gas and the room temperature oxygen gas contained in the atmosphere. There is no laser-type oxygen that detects the presence or absence of oxygen gas and measures the concentration only for oxygen gas contained in the gas to be measured by selecting a wavelength that is sensitive only to the high-temperature oxygen gas contained in the gas to be measured. A gas analyzer was developed. The prior art of such a laser type oxygen gas analyzer is disclosed, for example, in Patent Document 1 (Japanese Patent No. 5234381).

  The laser oxygen gas analyzer of Patent Document 1 uses the principle that the absorption intensity changes with temperature for all wavelengths that absorb gas (see FIGS. 2 and 4 of Patent Document 1). A laser oxygen gas analyzer used for combustion control uses detection light having a wavelength that has a high absorption intensity of oxygen gas at a high temperature and a low absorption intensity of oxygen gas at room temperature. By selecting such a wavelength, there is almost no sensitivity to the oxygen gas at normal temperature (around 25 ° C.) contained in the purge gas and the atmosphere, and the high temperature (400 ° C. or higher) contained in the combustion gas to be measured. In order to show the sensitivity only to the oxygen gas, the concentration ratio can be measured only for the oxygen gas contained in the measurement target gas, thereby improving the S / N.

Japanese Patent No. 5234381 (paragraphs [0035] to [0037], FIG. 2, FIG. 4, FIG. 5, etc.)

  The above-described laser oxygen gas analyzer may be used in a garbage incinerator using a gasification melting furnace. In this case, the laser-type oxygen gas analyzer with excellent environmental resistance such as response speed and dust is mainly used for high temperature gas combustion management. There is a need to measure change. As described above, depending on the application, there is a demand for measuring the gas concentration of oxygen gas in all regions from room temperature to high temperature.

  However, the laser-type oxygen gas analyzer of Patent Document 1 is intended to measure high-temperature oxygen gas of 400 ° C. or higher, and the gas concentration of oxygen gas in the entire temperature region including normal-temperature oxygen gas of less than 400 ° C. Could not be used in applications that want to measure

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to measure the gas concentration of oxygen gas in a wide range of temperatures using a plurality of wavelengths having different absorption intensities with respect to the gas temperature. The object is to provide an oxygen gas analyzer.

A laser type oxygen gas analyzer according to claim 1 of the present invention includes:
A light emitting unit that emits detection light by laser light, and a light receiving unit that receives detection light propagated through a space in which oxygen gas to be measured exists and calculates a gas concentration from the received signal intensity A laser oxygen gas analyzer for measuring the gas concentration of oxygen gas,
The light emitting part has a high temperature measurement wavelength laser light that has a high absorption intensity of high-temperature oxygen gas and a low absorption intensity of normal-temperature oxygen gas, and a wavelength adjacent to the high-temperature measurement wavelength at normal temperature. A laser beam having a wavelength for room temperature measurement that has a high absorption intensity of oxygen gas is emitted, and the light receiving unit includes a detection light for high temperature measurement absorbed by high temperature oxygen gas and oxygen at room temperature. The detection light for room temperature measurement absorbed by the gas is received, and the gas concentration of high-temperature oxygen gas is measured using the detection light for high temperature measurement. A laser oxygen gas analyzer characterized by measuring the gas concentration of oxygen gas was obtained.

Further, a laser type oxygen gas analyzer according to claim 2 of the present invention provides:
The laser oxygen gas analyzer according to claim 1,
The high temperature measurement wavelength is a wavelength of an absorption peak included in the range of 759.63 nm to 759.64 nm, and the normal temperature measurement wavelength is an absorption wavelength included in the range of 759.65 nm to 759.67 nm. A laser type oxygen gas analyzer characterized by having a peak wavelength or an absorption peak wavelength included in the range of 759.60 nm to 759.62 nm.

A laser oxygen gas analyzer according to claim 3 of the present invention is
In the laser type oxygen gas analyzer according to claim 2,
The light emitting unit emits a laser beam scanned at a scanning wavelength in a predetermined range including the high temperature measurement wavelength, and the light receiving unit receives a high temperature measurement detection light that is largely absorbed by a high temperature oxygen gas to be measured. Then, the gas concentration of the high-temperature oxygen gas is measured, and before and after the measurement of the gas concentration of the high-temperature oxygen gas, the light emitting unit is scanned with a scanning wavelength within a predetermined range including the wavelength for measuring the room temperature. A laser-type oxygen gas characterized in that it emits light and the light-receiving unit receives a detection light for normal temperature measurement that has been absorbed by the normal-temperature oxygen gas to be measured, and measures the gas concentration of the normal-temperature oxygen gas An analyzer was used.

A laser type oxygen gas analyzer according to claim 4 of the present invention includes:
In the laser type oxygen gas analyzer according to claim 2,
The light emitting unit emits a laser beam scanned at a scanning wavelength within a predetermined range including the high temperature measurement wavelength and the room temperature measurement wavelength, and the light receiving unit is largely absorbed by the high temperature oxygen gas to be measured. The high temperature measurement detection light and the high temperature detection light absorbed by the room temperature oxygen gas to be measured are received, and the gas concentration of the high temperature oxygen gas and the room temperature oxygen gas is measured. A laser oxygen gas analyzer was used.

  ADVANTAGE OF THE INVENTION According to this invention, the laser-type oxygen gas analyzer which measures the gas concentration of oxygen gas of a wide range temperature using the several wavelength from which absorption intensity differs with respect to gas temperature can be provided.

It is an absorption spectrum characteristic view of O ₂ gas. It is explanatory drawing of the example of a general absorption spectrum according to oxygen gas temperature. It is explanatory drawing of the absorption spectrum example according to oxygen gas temperature for combustion control. It is a block diagram of the laser type oxygen gas analyzer of the 1st Embodiment of this invention. It is a block diagram of a laser light source part. It is a figure which shows the output waveform of the wavelength scanning drive signal generation part of a laser element. For explaining the operation of the first embodiment of the present invention, it is a diagram showing a scanning waveform, absorption and output waveforms of the synchronous detector of the O ₂ gas laser device. It is a block diagram of a light receiving element and a signal processing part. It is a principle diagram of a wavelength modulation system. It is a figure which shows the change of the light emission wavelength of the semiconductor laser by a drive current. It is a figure which shows the change of the light emission wavelength of the semiconductor laser with temperature. For explaining the operation of the second embodiment of the present invention, it is a diagram showing a scanning waveform, absorption and output waveforms of the synchronous detector of the O ₂ gas laser device. For explaining the operation of the second embodiment of the present invention, it is a diagram showing a scanning waveform, absorption and output waveforms of the synchronous detector of the O ₂ gas laser device. For explaining the operation of the third embodiment of the present invention, it is a diagram showing a scanning waveform, absorption and output waveforms of the synchronous detector of the O ₂ gas laser device. For explaining the operation of the third embodiment of the present invention, it is a diagram showing a scanning waveform, absorption and output waveforms of the synchronous detector of the O ₂ gas laser device. It is a block diagram of the laser type oxygen gas analyzer of the 4th Embodiment of this invention. It is a block diagram of a laser light source part. It is a block diagram of a light receiving element and a signal processing part. It is explanatory drawing of the trigger signal sent to the output waveform of the wavelength scanning drive signal generation part of a laser element, and a signal processing part. It is a figure which shows the output signal of an I / V conversion part and a synchronous detection part. It is a figure which shows the output signal of an I / V conversion part and a synchronous detection part. It is a figure which shows the output signal of a synchronous detection part. It is an absorption spectrum characteristic view of O ₂ gas. It is explanatory drawing explaining the flow of purge gas.

Next, the laser oxygen gas analyzer of the present invention will be described below. First, the detection principle that characterizes the present invention will be described.
FIG. 1 shows an absorption spectrum of oxygen gas (O ₂ gas). Each of the oxygen gas absorption lines is represented by a linear spectrum. Oxygen gas absorbs light of a predetermined wavelength.

  Here, the point that the signal intensity obtained by the Lambert-Beer law is determined by the gas concentration and the distance at which the gas exists will be described. The Lambert-Beer equation is shown in Equation 1 below.

[Equation 1]
I (L) = I (0) · exp [−ks · ns · Ls]
I (L): received light quantity ks: gas coefficient
I (0): Light emission quantity ns: Gas concentration
Ls: Flue or cell length

  The signal intensity has parameters of gas coefficient ks, gas concentration ns, flue or cell length Ls. The gas coefficient ks is a value specific to the gas, and the flue or cell length Ls is a constant determined by design. That is, if the received light quantity I (L) can be measured, the gas concentration ns is calculated.

  Even when light of the same wavelength is absorbed by oxygen gas, the absorption intensity depends on temperature. In general, as shown in the absorption spectrum according to oxygen gas temperature in FIG. 2, even when the gas concentration is the same, the absorption intensity increases when the temperature of the oxygen gas is normal, and the apparent gas concentration is detected at the time of detection. Rises.

  However, as shown in the absorption spectrum for each oxygen gas temperature in FIG. 3, when the temperature of the oxygen gas increases at a certain wavelength, the absorption intensity rises exceptionally, and the apparent gas concentration increases at the time of detection. To do.

  Therefore, when measuring a change in the gas concentration of oxygen gas at room temperature, which is relatively low, such as when the furnace is started up, the gas is measured when the temperature of the oxygen gas is low, as in the oxygen absorption line spectrum of FIG. Detection is performed with detection light of a laser beam having an absorption wavelength having a high concentration intensity (hereinafter, a wavelength for normal temperature measurement). Further, when measuring the change in the gas concentration of the high-temperature oxygen gas to be used in combustion control, the absorption intensity of the gas concentration when the temperature of the oxygen gas is high as in the oxygen absorption line spectrum of FIG. Detection is performed using detection light of a laser beam having a large absorption wavelength (hereinafter referred to as a high temperature measurement wavelength). Hereinafter, description will be made by dividing into normal temperature and high temperature.

First, the wavelength for high temperature measurement will be described.
The wavelength for high temperature measurement is a wavelength of an absorption peak included in a predetermined range of 759.63 nm to 759.64 nm. The characteristic of the absorption line at this wavelength is that, as shown in FIG. 3, oxygen is hardly absorbed near room temperature, but oxygen is absorbed when the gas temperature is increased, and a high temperature of 400 to 1200 ° C. 400 ° C. or higher is referred to as high temperature, and in the present specification, less than 400 ° C., which is not high temperature, will be described as uniformly room temperature.

  The laser oxygen gas analyzer performs gas purging to protect the apparatus from heat in the furnace and to prevent adhesion of dust. Therefore, room temperature oxygen gas contained in the measurement target gas includes room temperature oxygen gas in instrument air contained in the purge gas.

  Such room-temperature oxygen gas is prevented from affecting the high-temperature oxygen gas to be measured. By using the temperature difference between the purge gas and the oxygen gas contained in the atmosphere and the oxygen gas contained in the measurement target gas, there is little sensitivity to the normal temperature oxygen gas contained in the purge gas and the atmosphere. The detection of the presence / absence of oxygen gas and the concentration measurement are performed only for the high-temperature oxygen gas contained in the measurement target gas so as to show sensitivity only to the high-temperature oxygen gas contained in the measurement target gas.

  Therefore, in a laser type oxygen gas analyzer, for example, in a garbage incineration facility, oxygen gas is detected near room temperature of less than 400 ° C. by detecting at a wavelength at which light absorption by oxygen gas occurs when the gas temperature increases. Since the absorption of light due to is not generated, it is possible to efficiently measure only the gas concentration of high-temperature oxygen gas of 400 ° C. or higher among the measurement target gas in the boiler without being affected by oxygen gas at room temperature. it can. Even if air is used as the purge gas, the S / N ratio does not decrease so as to greatly affect the accuracy.

Next, the room temperature measurement wavelength will be described.
As the wavelength for normal temperature measurement, for example, either the absorption peak wavelength included in the range of 759.65 nm to 759.67 nm or the absorption peak wavelength included in the range of 759.60 nm to 759.62 nm is adopted. Is done. The predetermined range 759.65 nm to 759.67 nm or the predetermined range 759.60 nm to 759.62 nm including the normal temperature measurement wavelength is adjacent to the predetermined range 759.63 nm to 759.64 nm including the high temperature measurement wavelength. As shown in FIG. 2, the absorption line at this normal temperature measuring wavelength hardly absorbs oxygen near a high temperature (400 ° C. or higher), but the gas temperature is normal temperature (less than 400 ° C., for example, 0 ° C. or 25 ° C. The absorption intensity of oxygen is sufficiently large at about ° C).

  At room temperature, there is oxygen gas at room temperature below 400 ° C. in the instrument air used for purge gas. Here, as is clear from FIG. 2, the absorption intensity is greatly different between 0 ° C. and 100 ° C., and the absorption intensity is determined in consideration of the temperature. The room temperature oxygen gas in the purge gas is also affected by the temperature of the furnace. The temperature inside the furnace is measured with a thermometer (not shown), and the average temperature of the purge gas is obtained by keeping the flow rate of the purge gas constant. It is possible to calculate the absorption intensity according to the temperature. In addition, it may be treated as a constant absorption intensity assuming that the temperature is constant at room temperature.

  Taking these into consideration, the absorption intensity of the oxygen gas concentration in the purge gas can be obtained from the product of the gas concentration of 20.6 vol% of the oxygen gas in the air and the length of the phase flange installed in the flue. Therefore, by subtracting the absorption intensity value of the oxygen gas in the air in the purge gas from the absorption intensity value of the normal temperature oxygen gas that is the measured value, the gas concentration of the normal temperature oxygen gas in the furnace at the time of startup of the furnace can be obtained. .

  In this way, the influence of the oxygen gas contained in the purge gas at both normal and high temperatures is eliminated, and the gas concentration of only the normal temperature oxygen gas to be measured or the gas concentration of only the high temperature oxygen gas can be detected. Become. The detection principle is like this.

  Next, a laser oxygen gas analyzer according to a first embodiment for carrying out the present invention will be described below with reference to the drawings. FIG. 4 is a configuration diagram of the laser oxygen gas analyzer 1 of the present embodiment. The laser oxygen gas analyzer 1 includes a light emitting unit 100, a light receiving unit 200, a light emitting unit side purge unit 300, and a light receiving unit side purge unit 400.

The light emitting unit 100 further includes a laser light source unit 101, a collimating lens 102, and a box cover 103.
The light receiving unit 200 includes a condenser lens 201, a light receiving element 202, a signal processing unit 203, and a box cover 204.

The light emission unit side purge unit 300 includes a purge unit main body 301, an inlet 302, and an outlet 303.
The light receiving unit side purge unit 400 includes a purge unit main body 401, an inflow port 402, and an outflow port 403.

In the laser-type oxygen gas analyzer of this embodiment, a specific example will be described on the assumption that a measurement target gas containing oxygen gas is fixed to a pipe such as a flue that passes through the inside. The measurement target gas is, for example, exhaust gas generated during combustion.
The walls 501a and 501b are walls of this pipe. The phase flanges 502a and 502b are fixed to the walls 501a and 501b by, for example, welding.

  The purge unit main body 301 of the light emitting unit side purge unit 300 including the angle adjustment mechanism unit is attached to one of the companion flanges 502a. The box cover 103 of the light emitting unit 100 is attached to the purge unit main body 301 of the light emitting unit side purge unit 300. The internal passage of the light emitting unit side purge unit 300 communicates with the internal passage of the companion flange 502a, and further communicates with the inside of the pipe. The box cover 103 and the internal passage of the companion flange 502a are separated by a window (not shown).

  The purge portion main body 401 of the light receiving portion side purge portion 400 including the angle adjusting mechanism portion is attached to the other phase flange 502b. A box cover 204 of the light receiving unit 200 is attached to the purge unit main body 401 of the light receiving unit side purge unit 400. The internal passage of the light receiving unit side purge unit 400 communicates with the internal passage of the phase flange 502b, and further communicates with the inside of the pipe. The box cover 204 and the internal passage of the companion flange 502b are separated by a window (not shown).

  A box cover 103 of the light emitting unit 100 includes a laser light source unit 101 mounted on an electronic substrate and a collimating lens 102 which is an optical component. Laser light emitted from the laser light source unit 101 is collimated into parallel light by the collimating lens 102. The collimated detection light 600 is incident on the inside of the walls 501a and 501b (inside the flue) through the center of the inner passage of the light emitting portion side purge portion 300 and the inner passage of the companion flange 502a.

The detection light 600 having the high-temperature measurement wavelength is absorbed when it passes through the oxygen gas in the measurement target gas inside the walls 501a and 501b. Further, when oxygen gas to be measured is present in the interior of the companion flanges 502 a and 502 b, the internal passage of the light emitting unit side purge unit 300, and the internal passage of the light receiving unit side purge unit 400, absorption is similarly performed.
Further, the detection light 600 having the measurement wavelength for normal temperature is absorbed when it passes through the oxygen gas in the purge gas or the low-temperature oxygen gas in the furnace.

  The detection light 600 is incident on the light receiving unit 200. The box cover 204 of the light receiving unit 200 includes a condenser lens 201 that is an optical component, a light receiving element 202 mounted on an electronic substrate, and a signal processing unit 203. The detection light 600, which is parallel light transmitted through the walls 501a and 501b (inside the flue), passes through the center of the internal passage of the companion flange 502b and the internal passage of the light-receiving unit-side purge unit 400, and the inside of the box cover 204. The light is condensed by the condenser lens 201 and received by the light receiving element 202. This light is converted into an electrical signal by the light receiving element 202 and input to the signal processing unit 203 at the subsequent stage.

  At this time, in order to prevent heat, corrosion, and contamination due to the measurement target gas, instrument air, which is compressed air, flows into the purge unit main body 301 from the inlet 302 into the light emitting unit side purge unit 300, and the light emitting unit side purge unit 300 The internal passage 300 is purged, and the internal passage of the companion flange 502 a is purged through the outlet 303. After this purging, the purge gas is discharged into the walls 501a and 501b (inside the flue). Similarly, instrument air, which is compressed air, flows into the light receiving unit side purge unit 400 from the inlet 402 into the purge unit main body 401, purges the internal passage of the light receiving unit side purge unit 400, and passes through the outlet 403. Then, the internal passage of the companion flange 502b is purged. After this purging, the purge gas is discharged into the walls 501a and 501b (inside the flue).

  The instrument air blows away dust and the like contained in the measurement target gas and adhered to each part, and keeps the window surfaces (not shown) of the light emitting unit 100 and the light receiving unit 200 clean. In addition, the instrument air flowing in for purge is at a normal temperature (for example, 25 ° C.), and the inside of the purge unit main bodies 301 and 401 and the phase flanges 502a and 502b are forcibly cooled.

  Next, detailed configurations of the light emitting unit 100 and the light receiving unit 200 will be described. First, the light emitting unit 100 will be described in detail with reference to FIGS. FIG. 5 shows details of the laser light source unit 101. The laser light source unit 101 includes a laser drive signal generation unit 101s having a wavelength scanning drive signal generation unit 101a and a high frequency modulation signal generation unit 101b.

The wavelength scanning drive signal generator 101a outputs a wavelength scanning drive signal for making the emission wavelength of the laser element variable so as to scan the absorption wavelength of the high-temperature or normal-temperature oxygen gas that is the measurement target gas.
The high-frequency modulation signal generation unit 101b outputs a high-frequency modulation signal for wavelength-modulating the wavelength with a sine wave of about 10 kHz, for example, in order to detect the absorption wavelength of the high-temperature or normal-temperature oxygen gas that is the measurement target gas.

  The wavelength scanning drive signal output from the wavelength scanning drive signal generation unit 101a is combined with the high frequency modulation signal from the high frequency modulation signal generation unit 101b to perform wavelength modulation to generate a laser drive signal. ing. The laser drive signal output from the laser drive signal generation unit 101s is converted into a current by the current control unit 101c and supplied to the laser element 101e made of a semiconductor laser. The laser element 101e is, for example, a laser element called a DFB laser (Distributed Feedback Laser) or a VCSEL (Vertical Cavity Surface Emitting Laser).

  The laser element 101e is provided with a temperature stabilizing means. This temperature stabilization means includes a temperature control unit 101d, a thermistor 101f, and a Peltier element 101g. A thermistor 101f as a temperature detecting element is disposed in the vicinity of the laser element 101e, and a Peltier element 101g is disposed in the vicinity of the thermistor 101f. The Peltier element 101g is subjected to PID (proportional / integral / differential) control by the temperature control unit 101d so that the resistance value of the thermistor 101f becomes a constant value, and as a result, the temperature of the laser element 101e is stabilized. It is what makes it operate.

  Here, as shown in FIG. 6, the wavelength scanning drive signal output from the wavelength scanning drive signal generation unit 101a becomes a substantially trapezoidal unit waveform due to the variable drive signal S1 and the offset signal S2. Is a signal repeated at a constant period.

  The variable drive signal S1 of the wavelength scanning drive signal is a signal for scanning the absorption wavelength, and is a part that linearly changes the magnitude of the current supplied to the laser element 101e via the current control unit 101c. This signal S1 is a signal for scanning the absorption wavelength by gradually shifting the emission wavelength of the laser element 101e. The emission wavelength can be scanned in the sub-nm to several nm range according to the slope of the signal S1, that is, the amount of change in the supply current. For example, in the case of oxygen gas, it is a portion that can scan a line width of about 0.02 nm.

The offset signal S2 of the wavelength scanning drive signal is an offset portion that does not scan the absorption wavelength but causes the laser element 101e to emit light, and has a value equal to or greater than a threshold current value at which the light emission of the laser element 101e of the light source unit 101 is stabilized. 101 is set to be supplied to the laser element 101e. The signal S1 and the signal S2 are inserted so as to be switched alternately.
The signal S3 is a portion where the drive current is almost zero.

Next, light emission by the light emitting unit 100 will be described.
First, the temperature of the laser element 101e is detected in advance by the thermistor 101f. Further, the temperature control unit 101d allows the Peltier element 101g to be measured so that the oxygen gas as the measurement target gas can be measured at the central portion of S1 of the wavelength scanning drive signal shown in FIG. 6 (so that a predetermined absorption characteristic can be obtained). The temperature of the laser element 101e is adjusted by controlling energization. Thereafter, the laser element 101e is driven.

FIG. 7 shows a drive signal for the laser element when oxygen gas is detected. First, description will be made assuming that high-temperature oxygen gas is detected. The frequency of the high frequency modulation signal is 10 kHz, the frequency of the wavelength scanning drive signal is 50 Hz, λ ₁ is a wavelength corresponding to the offset, λ ₂ (759.63 nm), λ ₄ (759.64 nm) are high-temperature oxygen gas (O The upper and lower limit values of the scanning wavelength corresponding to the absorption wavelength of ( ₂ gas), λ ₃ indicates the wavelength of the peak of the absorption waveform.
The laser element 101e irradiates the collimating lens 102 with the laser light that changes from the wavelength λ ₂ (759.63 nm) to λ ₄ (759.64 nm) in this way to generate the detection light 600 that is parallel light, and the measurement target gas The detection light 600 is emitted into the internal space of the walls 501 a and 501 b where the light is present, and the condensed light is incident on the light receiving element 202.

  Next, the light receiving unit 200 will be described. FIG. 8 shows the configuration of the light receiving element 202 and the signal processing unit 203. The signal processing unit 203 further includes an I / V conversion unit 203a, a synchronous detection unit 203b, an oscillator 203c, a filter 203d, and a calculation unit 203e.

  The light receiving element 202 is configured by a photodiode, for example, and a light receiving element having sensitivity to the light emission wavelength of the laser element 101e of the light emitting unit 100 is used. The output current of the light receiving element 202 is input to the I / V conversion unit 203a. The output current of the light receiving element 202 is converted into a voltage by the I / V conversion unit 203a. The output signal of the I / V conversion unit 203a is input to the synchronous detection unit 203b. The 2f signal from the transmitter 203c is added to the synchronous detection unit 203b, and a gas waveform signal obtained by extracting only the amplitude of the second harmonic signal having the same phase of the emitted light is obtained. The output signal of the synchronous detection unit 203b is sent to a calculation unit 203e such as a CPU through a noise removal filter 203d. The calculation unit 203e detects the presence or absence of oxygen gas and calculates the gas concentration of oxygen gas by various processes described below.

Here, the measurement principle of the wavelength modulation type laser oxygen gas analyzer will be described with reference to the principle diagram of the wavelength modulation type of the laser type oxygen gas analyzer of FIG. As shown in the absorption spectrum of oxygen gas (O ₂ gas) in FIG. 1, since the absorption line of this oxygen gas is represented by a linear spectrum, concentration detection by a wavelength modulation method is possible. Then, this laser type oxygen gas analyzer wavelength modulation scheme, center wavelength f _c, the output light of the semiconductor laser element and a wavelength modulation at the modulation frequency f _m, is irradiated to the oxygen gas to be measured. Here, the wavelength modulation is to modulate the waveform of the drive current supplied to the laser element 101e into a sine wave.

  In this wavelength modulation method, the gas concentration is measured by emitting only a single wavelength laser beam using a distributed feedback semiconductor laser (DFB laser) or a vertical cavity surface emitting laser (VCSEL) as described above. In this case, since the spectral line width at which the laser element emits light is smaller than the absorption line width of the measurement target gas, it is necessary to match the emission wavelength of the laser with the absorption wavelength of the measurement target gas. Therefore, the emission wavelength is controlled by controlling the temperature and current of the laser element.

  As shown in FIGS. 10 and 11, the laser element has an emission wavelength that varies depending on drive current and temperature. Since the laser element can emit a specific wavelength according to a constant value of temperature and current, it can be adjusted to the absorption wavelength according to a preset temperature and current value. Then, by performing wavelength modulation, the emission wavelength is modulated with the modulation of the drive current.

  As described above, the wavelength of the semiconductor laser element can be changed depending on the current and temperature, but the wavelength range is several nm, and it is necessary to use a laser element that emits light in the vicinity of the absorption wavelength of the measurement target gas. Due to the wavelength-selective nature of this laser element, all absorption lines as shown in FIG. 1 cannot be measured, and the absorption lines used for measurement have a relatively large absorption intensity and One or two absorptions do not overlap.

As shown in FIG. 9, since the absorption lines of the gas is almost quadratic function with respect to the modulation frequency, the absorption line plays the role of a discriminator, the light receiving portion of the double modulation frequency f _m A frequency signal (second harmonic signal) is obtained. Since the modulation frequency f _m good at any frequency, for example, using Selecting a modulation frequency f _m to several kHz, a digital signal processing device (DSP) or general-purpose processor, extraction of the second harmonic signal It is possible to perform advanced signal processing such as.

  Further, if the envelope detection is performed by the light receiving unit, the fundamental wave by amplitude modulation can be estimated, and the ratio between the amplitude of the fundamental wave and the amplitude of the second harmonic signal is detected in phase synchronization, so that it exists in addition to the concentration. A signal proportional to the gas concentration to be measured can be obtained without being affected by the signal having the same frequency component.

  Based on such a principle, when there is no absorption of the laser beam by the measurement target gas, the synchronous detection unit 203b does not detect the second harmonic signal, and therefore the output of the synchronous detection unit 203b is almost a straight line.

  On the other hand, when there is absorption of laser light by the measurement target gas, the synchronous detection unit 203b detects a second harmonic signal that is a signal obtained by extracting only the amplitude of the second frequency component of the modulation signal of the emitted light. The output waveform is the peak waveform of the synchronous detection unit 203b shown in the dotted circle in FIG. Noise is removed from the peak waveform by the filter 203d, and the peak waveform is appropriately amplified and output to the arithmetic unit 203e such as a CPU or DSP in the subsequent stage. The calculation unit 203e detects the presence or absence of oxygen gas and calculates the gas concentration of oxygen gas by various processes described below.

  The calculation unit 203e functions as follows. First, the peak waveform in the dotted circle in FIG. 7 is a portion (gas absorption waveform A) that has been absorbed by the measurement target gas, and the maximum value or minimum value of this gas absorption waveform A is the concentration of the measurement target gas. Equivalent to. Therefore, the calculation unit 203e measures the peak value of the waveform corresponding to the concentration of the measurement target gas using the gas absorption waveform A that is the output of the synchronous detection unit 203b shown in the circle of FIG. As a means for measuring the amplitude difference between the maximum value and the minimum value of the absorption waveform A, or integrating part or all of the gas absorption waveform A and detecting the concentration of oxygen gas to be measured from the integrated value. Function. Also, it functions as means for determining that there is no oxygen gas when the gas concentration is lower than a predetermined value.

  A converter (not shown) is connected to the calculation unit 203e. The converter corrects the concentration converted by the calculation unit 203e to a concentration value corresponding to a change in gas temperature or gas pressure, and a display unit that displays the concentration value corrected by the correction unit on the display. And an external transmission unit for transmitting the analog density value and digital signal. The calculation unit 203e performs output control, and the density value corrected by the correction function display unit is displayed on the display unit. Detection of high-temperature oxygen gas is performed in this way.

Next, detection at normal temperature will be described. This differs only in that the scanning wavelengths are different. FIG. 7 shows the drive signal of the laser element, the frequency of the high frequency modulation signal is 10 kHz, the frequency of the wavelength scanning drive signal is 50 Hz, λ ₁ is the wavelength corresponding to the offset, λ _{2 to} λ ₄ (759.60 nm). ˜759.62 nm or 759.65 nm to 759.67 nm) is the upper and lower limit values of the scanning wavelength corresponding to the absorption wavelength of oxygen gas at room temperature, and λ ₃ is the wavelength of the peak of the absorption waveform. Laser element 101e is irradiated with laser light to change the wavelength lambda ₂ to lambda _4. Hereinafter, the signal processing in the latter stage is to detect the gas concentration of the oxygen gas at room temperature in the same manner, and redundant description is omitted. The gas concentration of oxygen gas at room temperature is acquired as such a wavelength.

  Here, there is room temperature oxygen gas of less than 400 ° C. in the instrument air used for purge gas at room temperature, but the absorption strength of the oxygen gas concentration in the purge gas is 20.6 vol of oxygen gas concentration in the air. % And the product of the length of the companion flange installed in the flue. Therefore, the concentration of the oxygen gas at normal temperature in the furnace at the time of starting up the furnace is obtained by subtracting the absorption intensity value of the oxygen gas in the purge gas from the absorption value of the normal temperature oxygen gas that is the measured value. Can do.

  In this embodiment, it has been described that, following the measurement of high-temperature oxygen gas, room-temperature oxygen gas such as purge gas is detected. However, it is also possible to first measure room temperature oxygen gas contained in the air in the furnace when the furnace is started up, and then detect high temperature oxygen gas. Either measurement of normal temperature oxygen gas following measurement of high temperature oxygen gas or measurement of high temperature oxygen gas following measurement of normal temperature oxygen gas can be selected.

  The first embodiment has been described above. In the prior art, the oxygen gas contained in the purge gas and the atmosphere and the oxygen gas contained in the measurement target gas cannot be distinguished from each other and are measured together, which is difficult in terms of reliability. On the other hand, in the present invention, by utilizing the temperature difference between the oxygen gas contained in the purge gas and the atmosphere and the oxygen gas contained in the measurement target gas, the room temperature oxygen gas contained in the purge gas and the atmosphere, and A laser that detects the presence of oxygen gas contained in the measurement target gas and room temperature oxygen gas at the time of startup of the furnace and measures the concentration so that each high-temperature oxygen gas contained in the measurement target gas exhibits sensitivity. Type oxygen gas analyzer. Thereby, the gas concentration measurement of 0-1200 degreeC oxygen gas can be measured with one apparatus.

  Next, a second embodiment of the present invention will be described with reference to the drawings. Compared with the embodiment described with reference to FIGS. 1 to 11 in this embodiment, the scanning wavelength shown in FIGS. 12 and 13 is adopted instead of the scanning wavelength shown in FIG. The difference is that the concentration measurement of oxygen gas at normal temperature and high temperature is terminated. Hereinafter, only the scanning wavelength will be described, and the calculation of the apparatus configuration and the gas concentration is the same as in the first embodiment, and redundant description is omitted.

  Laser wavelength scanning in the laser oxygen gas analyzer of this embodiment will be described. As shown in FIG. 6 described above, the wavelength scanning drive signal is a signal having a substantially trapezoidal unit waveform due to the variable drive signal S1 and the offset signal S2, and such a unit waveform is repeated at a constant period.

  The variable scanning signal S1 of the wavelength scanning driving signal is a signal for scanning the absorption wavelength, and is a part that linearly changes the magnitude of the current supplied to the laser element. This signal S1 is a signal for scanning the absorption wavelength by gradually shifting the emission wavelength of the laser element. The emission wavelength can be scanned in the sub-nm to several nm range according to the slope of the signal S1, that is, the amount of change in the supply current. For example, in the case of a high-temperature oxygen gas and a room-temperature oxygen gas, it is a portion that can scan a line width of about 0.05 nm.

Next, FIG. 12 shows the drive signal of the laser element, the frequency of the high frequency modulation signal is 10 kHz, the frequency of the wavelength scanning drive signal is 50 Hz, λ ₁ is the wavelength corresponding to the offset, and λ ₂ and λ ₅ are room temperature. The upper and lower limits of the scanning range including the absorption wavelength of high-temperature oxygen gas, λ ₃ is the peak wavelength of the absorption waveform where oxygen gas is absorbed only at high temperature, and λ ₄ is the absorption waveform where oxygen gas is absorbed only at normal temperature. The peak wavelength is shown.

For example, λ ₂ to λ ₅ (759.63 nm to 759. 759) including both the predetermined range for detecting high temperature 759.63 nm to 759.64 nm and the predetermined range for detecting normal temperature 759.65 nm to 759, 67 nm. 67 nm). The scanning wavelength range is expanded to 0.04 to 0.05 nm.
The laser element 101e irradiates the collimating lens 102 with the laser light changing from the wavelength λ ₂ (759.63 nm) to λ ₄ (759.67 nm) in this way, and emits the detection light 600 that is parallel light.

  The output waveform of the synchronous detector when there is both room temperature oxygen gas and high temperature oxygen gas is a peak waveform of two peaks as shown in the lower part of FIG. Further, the output waveform of the synchronous detector when there is only oxygen gas at room temperature is a peak waveform of one peak as shown in the lower part of FIG. In this way, the scanning is performed by changing the wavelength little by little to measure the gas concentration of oxygen gas at normal temperature and high temperature in one measurement, and the gas concentration of oxygen gas from 0 to 1200 ° C. is measured. .

  In this way, the laser wavelength scanning range is expanded, and a single scan with a wide range of scanning wavelengths including a wavelength with a high absorption intensity of oxygen gas at room temperature and a wavelength with a high absorption intensity of high-temperature oxygen gas. By scanning, it is possible to provide a laser type oxygen gas analyzer that measures oxygen gas in a wide range of 0 to 1200 ° C.

  Next, a third embodiment of the present invention will be described with reference to the drawings. Compared with the embodiment described with reference to FIGS. 1 to 11 in this embodiment, the scanning wavelength shown in FIGS. 14 and 15 is employed instead of the scanning wavelength shown in FIG. The difference is that the measurement is terminated. Hereinafter, only the scanning wavelength will be described, and the calculation of the apparatus configuration and the gas concentration is the same as in the first embodiment, and redundant description is omitted.

  Laser wavelength scanning in the laser oxygen gas analyzer of this embodiment will be described. As shown in FIG. 6 described above, the wavelength scanning drive signal is a signal having a substantially trapezoidal unit waveform due to the variable drive signal S1 and the offset signal S2, and such a unit waveform is repeated at a constant period.

  The variable scanning signal S1 of the wavelength scanning driving signal is a signal for scanning the absorption wavelength, and is a part that linearly changes the magnitude of the current supplied to the laser element. This signal S1 is a signal for scanning the absorption wavelength by gradually shifting the emission wavelength of the laser element. The emission wavelength can be scanned in the sub-nm to several nm range according to the slope of the signal S1, that is, the amount of change in the supply current. For example, in the case of a high-temperature oxygen gas and a room-temperature oxygen gas, it is a portion that can scan a line width of about 0.05 nm.

Next, FIG. 14 shows the drive signal of the laser element, the frequency of the high frequency modulation signal is 10 kHz, the frequency of the wavelength scanning drive signal is 50 Hz, λ ₁ is the wavelength corresponding to the offset, and λ ₂ and λ ₅ are Upper and lower limits of the scanning range including the absorption wavelength of oxygen gas at high temperature and normal temperature, λ ₃ is the wavelength of the peak of the absorption waveform where oxygen gas is absorbed only at normal temperature, and λ ₄ is the absorption where oxygen gas is absorbed only at high temperature The wavelength of the peak of the waveform is shown.

For example, λ ₂ to λ ₅ (759.60 nm to 759.59) including both the predetermined range for normal temperature detection 759.60 nm to 759.62 nm and the predetermined range for high temperature detection 759.63 nm to 759.64 nm. 64 nm). The scanning wavelength range is expanded to 0.04 to 0.05 nm.
The laser element 101e irradiates the collimator lens 102 with the laser light changing from the wavelength λ ₂ (759.60 nm) to λ ₄ (759.64 nm) in this way, and emits the detection light 600 that is parallel light.

  The output waveform of the synchronous detector when there is both room temperature oxygen gas and high temperature oxygen gas is a peak waveform of two peaks as shown in the lower part of FIG. Further, the output waveform of the synchronous detector when there is only oxygen gas at room temperature is a peak waveform of one peak as shown in the lower part of FIG. In this way, the scanning is performed by changing the wavelength little by little to measure the gas concentration of oxygen gas at normal temperature and high temperature in one measurement, and the gas concentration of oxygen gas from 0 to 1200 ° C. is measured. .

  In this way, the laser wavelength scanning range is expanded, and a single scan with a wide range of scanning wavelengths including a wavelength with a high absorption intensity of oxygen gas at room temperature and a wavelength with a high absorption intensity of high-temperature oxygen gas. By scanning, a laser oxygen gas analyzer capable of measuring a wide range of oxygen gas from 0 ° C. to 1200 ° C. can be provided.

  Next, a fourth embodiment of the present invention will be described with reference to the drawings. Compared with the previous first embodiment, this embodiment basically has the same configuration as that in FIG. 4, but as shown in FIG. 16, the laser light source unit 101 ′ of the light emitting unit 100 and the light receiving unit The signal processing unit 203 ′ is connected to the 200 signal processing unit 203 ′ through a light emitting unit / light receiving unit line 700 so as to be communicable. Further, the difference is that the signal processing unit 203 ′ of the light receiving unit 200 and the control unit 900 are communicably connected by the light receiving unit / control unit line 800.

  Specifically, as shown in FIG. 17, the trigger signal S4 (see FIG. 19) of the wavelength scanning drive signal is extracted and output from the wavelength scanning drive signal generation unit 101a of the laser light source unit 101 ′, and FIG. As shown by, the calculation unit 203e of the signal processing unit 203 ′ receives the trigger signal S4 and is synchronized using the trigger signal S4 (see FIG. 20). The laser light source unit 101 ′ of the light emitting unit 100 in FIG. 17 and the signal processing unit 203 ′ of the light receiving unit 200 in FIG. 18 are compared with the laser light source unit 101 in FIG. 5 and the signal processing unit 203 in FIG. Although it has the same configuration, it is different in that the trigger signal S4 is input and output, and the calculation unit 203e performs calculation processing based on the trigger signal S4. The other configuration has been described in the first embodiment. The same reference numerals as those in the configuration are attached and redundant description is omitted, and only the differences will be described.

  FIG. 19 is a diagram for explaining the trigger signal S4. The trigger signal S4 is input from the wavelength scanning drive signal generation unit 101a to the calculation unit 203e. As shown in the figure, the trigger signal S4 is a pulse signal output from the wavelength scanning drive signal generation unit 101a in synchronization with one cycle of the wavelength scanning driving signal including S1, S2, and S3. For example, the trigger signal S4 may be generated in synchronization with the timing of the wavelength scanning drive signal (the generation timing of the signal S3) that makes the drive current of the laser element 101e zero. A trigger signal S4 is output from the wavelength scanning drive signal generation unit 101a and input to the calculation unit 203e via the light emitting unit / light receiving unit line 700.

  Next, a method for calculating the concentration of oxygen gas by the calculation unit 203e of the signal processing unit 203 of this embodiment will be described. As shown in FIG. 17, in the laser light source unit 101, the temperature control unit 101d controls the energization of the Peltier element 101g so that the measurement target gas can be measured at the central portion of the wavelength scanning drive signal S1, and the temperature of the laser element 101e. Adjust. The laser element 101e is driven to emit laser light into the internal space of the walls 501a and 501b where the measurement target gas exists.

  The laser beam is condensed by the condensing unit 201 and the collected light is incident on the light receiving element 202. Measure oxygen gas as the gas to be measured. The light receiving element 202 converts it into a detection signal based on an electric signal according to the amount of received light and sends it to the signal processing unit 203. For example, the signal processing unit 203 performs amplification or noise filtering on the detection signal to detect the density. In the signal processing unit 203, when the laser light is not absorbed by the measurement target gas, as shown in FIG. 20, since the double frequency signal is not detected by the synchronous detection unit 203b, the output of the synchronous detection unit 203b is almost linear. Become.

  On the other hand, when there is absorption of laser light by the measurement target gas, the double frequency signal is detected by the synchronous detection unit 203b. FIG. 21 is a waveform diagram showing the output signal Sb of the synchronous detection unit 203b together with the output signal Sa of the I / V conversion unit 203a. In FIG. 21, the portion surrounded by the dotted line is the gas absorption waveform A. This shall detect hot oxygen gas. Note that detection of oxygen gas at room temperature is the same, and redundant description is omitted.

Here, when there is an offset in the output signal Sb of the synchronous detection portion 203b by some cause, as shown in FIG. 22, offset is not the original output signal Sb ₀ signal Sb ₁ appears added. As a result, an error occurs in the detection based on the maximum value or the minimum value of the gas absorption waveform A in FIG. 21 or the integral value of the waveform, and the gas concentration may not be detected accurately. Therefore, in this embodiment, the following method is used in order to detect the gas concentration with higher accuracy and stability.

  As described above, in the case shown in FIG. 20 where the measurement target gas does not exist, the double frequency signal is not detected by the synchronous detection unit 203b, and the output of the synchronous detection unit 203b becomes a substantially straight line. However, since various noises exist, even if the measurement target gas does not exist, the output signal Sb of the synchronous detection unit 203b has a slightly uneven waveform as shown in FIG. In the case of such a waveform, in a method of simply detecting only the maximum value or the minimum value of the waveform, there is a risk that the uneven portion due to noise is mistaken as a gas absorption waveform and the maximum value or the minimum value is detected erroneously. Similarly, when an integral value of a waveform is obtained, there is a possibility of erroneous detection. In particular, when the measurement target gas has a low concentration, the uneven portion becomes a large error factor when detecting the gas concentration.

  For this reason, in this embodiment, in order not to misidentify the uneven portion due to noise as the gas absorption waveform, the trigger signal S4 output from the wavelength scanning drive signal generator 204a as shown in FIG. Identifies the position where the maximum or minimum value should be. The trigger signal S4 is synchronized with one cycle of the wavelength scanning drive signal, and is particularly synchronized with S3 of the wavelength scanning drive signal. There is a certain temporal correlation between the trigger signal S4 and the output signal Sb of the synchronous detector 203b.

  That is, when the measurement target gas exists, the timing at which the gas absorption waveform A, the maximum value C, and the minimum values B and D in FIGS. 20 and 21 are generated with respect to the timing of the trigger signal S4 is detected almost accurately in advance. Is possible. Therefore, measurement is performed on the assumption that the minimum value B at point B, the maximum value C at point C, and the minimum value D at point D appear in the synchronous detector output waveform when a predetermined time tb, tc, td has elapsed from the trigger signal. . this. These predetermined times tb, tc, and td are preliminarily calculated experimentally before factory shipment or at the time of calibration, and are registered in a memory (not shown). The concentration is calculated using this value.

  When measuring the gas concentration, the synchronous detector at the predetermined times tb, tc and td at which the maximum value C and the minimum values B and D should be generated with reference to the trigger signal S4 received from the wavelength scanning drive signal generator 204a. The maximum value and the minimum value are measured from the output signal Sb of 203b (the output signal of the filter 203d).

  As a result, even when the concentration of the measurement target gas is as low as possible, the calculation unit 203e detects the gas absorption waveform A, the maximum value C, and the minimum values B and D based on the trigger signal S4. Functions as a means to The calculation unit 203e can accurately detect and measure these values. Therefore, the gas concentration can be calculated with high accuracy without being affected by the uneven portions of the waveform due to noise.

  The calculation unit 203e functions as a means for reading and storing the value of the synchronous detection unit output waveform when a predetermined time tb, tc, td elapses from the trigger signal, and thereafter calculating the concentration. For example, the maximum value at the peak of the waveform directly represents the gas concentration, so that the maximum value is output as the concentration. Alternatively, the difference value obtained by subtracting the minimum value from the maximum value is used as the density. The concentration is measured using these ABCD. The calculation unit 203e in FIG. 18 detects a maximum value C and minimum values B and D before and after the gas absorption waveform A shown in FIG. 21, and calculates a gas concentration by the following formula 2 or formula 3. Function as.

[Equation 2]
Oxygen gas concentration = α × | BC

[Equation 3]
Oxygen gas concentration = α × | CD |

  In Equations 2 and 3, α is a gas concentration conversion coefficient. The gas concentration conversion coefficient α is determined by calibrating in advance with a gas whose concentration of the measurement gas component is known. For example, the zero gas with the concentration of the measurement gas component of 0 ppm and the span gas with the concentration of the measurement gas component being the maximum concentration in the desired measurement range are measured, and the actual values of the zero gas and the span gas are measured as the first calibration point and the second calibration. A straight line connecting the two points is used as a reference calibration curve. The slope of the reference calibration curve is defined as a gas concentration conversion coefficient α. The oxygen gas concentration is calculated in this way. Further, in the case of the synchronous detection unit output as shown in FIG. 20, the oxygen gas concentration is equal to or lower than a predetermined value, and it is determined that there is no oxygen. The calculation unit 203e functions as means for performing such processing.

  In this embodiment, the calculation processing unit of the signal processing unit has been described as performing all signal processing, but the data is transmitted to the control unit 900 connected to the calculation processing unit by the light receiving unit / control unit line 800, It is good also as a structure which the control part 900 performs calculation. These configurations are appropriately selected. Further, in this embodiment, as in the first embodiment, the high-temperature oxygen gas concentration measurement and the normal-temperature oxygen gas concentration measurement are separately scanned. The scanning wavelength as shown in FIGS. 12 and 13 is adopted as in the embodiment, or the scanning wavelength as shown in FIGS. 14 and 15 is adopted as in the third embodiment. Alternatively, the measurement of the oxygen gas concentration at normal temperature and high temperature may be completed in one scan. In this case, the predetermined time tb, tc, td at which the maximum value C and minimum values B, D of the first peak should occur and the timing at which the maximum value F, minimum value E, G of the next peak should occur , Tf, tg are registered in advance and the gas concentration calculation process is performed in the same manner. These methods can be appropriately selected.

  The present embodiment has been described above. Compared to simply detecting the maximum value, minimum value, or integral value of the gas absorption waveform, the peak position can be accurately detected by synchronizing the trigger signal, so the detection capability of low-concentration gas is also improved. . If the said structure is employ | adopted, a measurement precision can be raised more.

In addition, since the loss is low, the peak can be surely displayed, and the detection ability of low concentration oxygen gas is improved.
In particular, it is synchronized with the timing of the wavelength scanning drive signal that makes the drive current of the laser element zero, and the synchronization signal can be discriminated.

  In particular, when the gas concentration is low, the effects of noise caused by interference of laser light from optical window materials and lenses, etc., become stronger, and these noises are detected as peaks, making it difficult to find peaks. However, in the present invention, since the portion where gas absorption occurs is set in advance and the gas absorption peak is detected based on the trigger signal, accurate gas concentration detection can be performed without being affected by noise or the like. There is an advantage.

  According to the present invention, in a process of measuring a low-temperature oxygen gas generated at startup of a furnace or a high-temperature oxygen gas at the time of combustion with a laser analyzer in a boiler or the like, without being affected by the gas component used for the purge gas, The gas concentration of the oxygen gas to be measured can be measured efficiently. The ability to use instrument air as the purge gas has great advantages in terms of introduction cost and operation cost.

Normally, when air is used as the purge gas, the amount of oxygen contained in the air is often sufficient to affect the amount of oxygen to be measured as a disturbance, and also to the oxygen gas concentration at room temperature. The absorption line having a large sensitivity tends to decrease the absorption intensity by about 40 to 80% at a high temperature of 400 ° C. or higher, and as a result, the S / N decreases and the measurement becomes difficult.
On the other hand, the present invention is not affected by the gas concentration of the oxygen gas in the air at normal temperature contained in the purge gas, and can accurately measure the gas concentration of the normal temperature or high temperature oxygen gas to be measured.

  In addition, according to the present invention, in a laser-type oxygen gas analyzer based on absorption spectroscopy using a semiconductor laser, the detection capability of low-concentration gas is improved by ensuring that a peak appears due to low loss. . Furthermore, by detecting the gas absorption peak based on the trigger signal of the wavelength scanning signal, the low concentration gas can be detected. Furthermore, by detecting the gas absorption peak in consideration of the influence of dust and the like, it has become possible to detect a lower concentration gas.

  In addition, according to the present invention, the gas concentration of oxygen gas at room temperature can be detected, so that the gas concentration of oxygen gas can be measured with high accuracy from room temperature to a high temperature region. Furthermore, by expanding the current drive range of the laser, the wavelength scanning range of the laser is expanded, and a plurality of oxygen gas absorption lines can be simultaneously measured. Multiple oxygen gas absorption lines select the optimum absorption line for each temperature range and measure oxygen gas, which also enables high-precision oxygen gas concentration measurement from room temperature to high temperature range. .

  The laser oxygen gas analyzer of the present invention is optimal for measuring combustion exhaust gas such as boilers and garbage incineration. In addition, gas analysis for steel [blast furnace, converter, heat treatment furnace, sintering (pellet equipment), coke oven], fruit and vegetable storage and ripening, biochemistry (microorganism) [fermentation], air pollution [incinerator, flue gas desulfurization / Denitration], automobile exhaust gas (remove tester), disaster prevention [explosive gas detection, toxic gas detection, new building material combustion gas analysis], plant growth, chemical analysis [oil refinery plant, petrochemical plant, gas generation plant], It is also useful as an analyzer for environmental [landing concentration, tunnel concentration, parking lot, building management], and various physics and chemistry experiments.

DESCRIPTION OF SYMBOLS 1,1 ': Laser type oxygen gas analyzer 100: Light emission part 101, 101': Laser light source part 101a: Wavelength scanning drive signal generation part 101b: High frequency modulation signal generation part 101c: Current control part 101d: Temperature control part 101e: Laser element 101f: Thermistor 101g: Peltier element 101s: Laser drive signal generation unit 102: Collimator lens 103: Box cover 200: Light receiving unit 201: Condensing lens 202: Light receiving element 203, 203 ′: Signal processing unit 203a: I / V Conversion unit 203b: synchronous detection unit 203c: oscillator 203d: filter 203e: calculation unit 204: box cover 300: light emission unit side purge unit 301: purge unit body 302: inflow port 303: outflow port 400: light receiving unit side purge unit 401: Purge part main body 402: Inlet 403: Outlet 501a, 501b: 502a, 502b: mating flange 600: Detection light 700: light emitting elements and the light-receiving section line 800: light receiving unit and control unit line 900: control unit

Claims (4)

A light emitting unit that emits detection light by laser light, and a light receiving unit that receives detection light propagated through a space in which oxygen gas to be measured exists and calculates a gas concentration from the received signal intensity A laser oxygen gas analyzer for measuring the gas concentration of oxygen gas,
The light emitting part has a high temperature measurement wavelength laser light that has a high absorption intensity of high-temperature oxygen gas and a low absorption intensity of normal-temperature oxygen gas, and a wavelength adjacent to the high-temperature measurement wavelength at normal temperature. A laser beam having a wavelength for room temperature measurement that has a high absorption intensity of oxygen gas is emitted, and the light receiving unit includes a detection light for high temperature measurement absorbed by high temperature oxygen gas and oxygen at room temperature. The detection light for room temperature measurement absorbed by the gas is received, and the gas concentration of high-temperature oxygen gas is measured using the detection light for high temperature measurement. A laser oxygen gas analyzer characterized by measuring a gas concentration of oxygen gas. The laser oxygen gas analyzer according to claim 1,
The high temperature measurement wavelength is a wavelength of an absorption peak included in the range of 759.63 nm to 759.64 nm, and the normal temperature measurement wavelength is an absorption wavelength included in the range of 759.65 nm to 759.67 nm. A laser type oxygen gas analyzer characterized by having a peak wavelength or an absorption peak wavelength included in a range of 759.60 nm to 759.62 nm. In the laser type oxygen gas analyzer according to claim 2,
The light emitting unit emits a laser beam scanned at a scanning wavelength in a predetermined range including the high temperature measurement wavelength, and the light receiving unit receives a high temperature measurement detection light that is largely absorbed by a high temperature oxygen gas to be measured. Then, the gas concentration of the high-temperature oxygen gas is measured, and before and after the measurement of the gas concentration of the high-temperature oxygen gas, the light emitting unit is scanned with a scanning wavelength within a predetermined range including the wavelength for measuring the room temperature. A laser-type oxygen gas characterized in that it emits light and the light-receiving unit receives a detection light for normal temperature measurement that has been absorbed by the normal-temperature oxygen gas to be measured, and measures the gas concentration of the normal-temperature oxygen gas Analyzer. In the laser type oxygen gas analyzer according to claim 2,
The light emitting unit emits a laser beam scanned at a scanning wavelength within a predetermined range including the high temperature measurement wavelength and the room temperature measurement wavelength, and the light receiving unit is largely absorbed by the high temperature oxygen gas to be measured. The high temperature measurement detection light and the high temperature detection light absorbed by the room temperature oxygen gas to be measured are received, and the gas concentration of the high temperature oxygen gas and the room temperature oxygen gas is measured. Laser oxygen gas analyzer.

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