JP5794167B2 - Gas analyzer - Google Patents

Description

  The present invention relates to a gas analyzer that measures the amount of water vapor in a gas using laser absorption spectroscopy, and more particularly in a vacuum region, in a flue, in a combustion process, in a vehicle measurement target gas, or in a fuel cell in a semiconductor manufacturing apparatus. The present invention relates to a gas analyzer that measures the amount of water vapor in a flow path or the like.

  One method for measuring the amount of water vapor in a gas is absorption spectroscopy using the fact that water molecules absorb only light in a specific wavelength region (eg, 1.3 μm band). Since this absorption spectroscopy can be measured without contact with the sample gas to be measured, the amount of water vapor in the sample gas can be measured without disturbing the field of the sample gas.

  Among such absorption spectroscopy methods, in particular, “wavelength tunable semiconductor laser absorption spectroscopy” using a wavelength tunable semiconductor laser as a light source can be realized with a simple apparatus configuration. For example, in a gas analyzer using “wavelength tunable semiconductor laser absorption spectroscopy”, an incident optical window formed in a pipe and an output for a pipe in which a sample gas flows in a predetermined direction (sample flow path) It is common to add a wavelength tunable semiconductor laser and a photodetection sensor (light receiving unit) provided to face each other so that an optical path (optical path length L) is formed across the pipe through an optical window. Yes (for example, see Patent Document 1 and Patent Document 2).

  According to such a gas analyzer, the laser light of a predetermined wavelength ν emitted from the wavelength tunable semiconductor laser is propagated by the shielding action of water molecules present in the sample gas in the process of passing through the pipe. Using the fact that the amount of light incident on the light detection sensor is reduced in response to the concentration of water molecules in the sample gas, it is incident on the light detection sensor for the amount of laser light emitted from the wavelength tunable semiconductor laser. The concentration of water molecules is calculated by measuring the amount of laser light. Thereby, the behavior of the sample gas actually occurring can be known in real time. Further, since the measurement sensitivity increases in proportion to the optical path length L, by selecting the optical path length L, it is possible to measure the amount of water vapor from the trace moisture amount region to the high humidity region.

  Here, an example of calculation processing in absorption spectroscopy will be described. From Lambert-Beer's law, the following formula (1) holds.

Here, I ₀ (ν) is the light intensity when the water molecule is not absorbed at the frequency ν, I (ν) is the transmitted light intensity at the frequency ν, c is the number density of the water molecules, and L passes through the sample gas. S (T) is a function of the gas temperature T at a predetermined absorption line intensity, and K (ν) is an absorption characteristic function at the frequency ν.

FIG. 5 is a schematic configuration diagram showing an example of a gas analyzer using wavelength tunable semiconductor laser absorption spectroscopy, and FIG. 6 is a block diagram of the gas analyzer shown in FIG. One direction horizontal to the ground is defined as an X direction, a direction horizontal to the ground and perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the X direction and the Y direction is defined as a Z direction.
The gas analyzer 101 includes a light source unit 10, a light receiving unit 20, a pressure sensor 31 that measures a pressure value _Ptotal , a gas temperature sensor 32 that measures a gas temperature value T, and a laser control unit that controls the light source unit 10. 50 and a control unit 160 composed of a microcomputer and a PC.

  Here, the gas analyzer 101 is used to measure the amount of water vapor in the measurement target gas flowing in the sample flow path 70 connected to each line of supply and exhaust to the fuel cell system. The sample flow path 70 extends in the Z direction, and on the side wall of the sample flow path 70, there are an incident optical window 71, and an output optical window 72 facing the incident optical window 71 with a distance L in the X direction. Is formed. The measurement target gas flows in the Z direction in the sample flow path 70.

The light source unit 10 is, for example, a distributed feedback (DFB) semiconductor laser diode for optical communication. The laser diode can adjust the oscillation wavelength ν of the laser within a predetermined wavelength range in the near infrared region, and is controlled by a control signal from the laser control unit 50. The light source unit may be a laser having any structure in the infrared or other wavelength region as long as it is a wavelength tunable semiconductor laser, and a quantum cascade laser or the like may be used although it is relatively expensive.
The laser diode is disposed so that laser light is incident in the X direction from the incident optical window 71 into the sample flow path 70, and the laser light is irradiated onto the measurement target gas. .

The light receiving unit 20 may be anything that can convert light intensity into an electrical signal, and is, for example, a photodiode. The photodiode is arranged so as to receive the laser light emitted in the X direction from the emission optical window 72 to the outside of the sample flow path 70, and the intensity I (ν) of the laser light that has passed through the measurement target gas. Is received. As a result, a spectral waveform including the intensity I (ν) of the laser beam at the center wavelength portion of the absorption spectrum of the water molecule and the intensity I ₀ (ν) of the laser light at the non-absorption wavelength portion on both sides of the center wavelength portion is obtained. By obtaining with a photodiode, the control unit 160 can calculate I ₀ (ν) and I (ν). FIG. 7 is a graph showing an example of an absorption spectrum acquired by a photodiode.

The pressure sensor 31 is installed in the sample flow path 70, and measures a pressure value _Ptotal that is the total pressure of the measurement target gas at predetermined time intervals. The gas temperature sensor 32 is also installed in the sample flow path 70 and measures a gas temperature value T, which is the temperature of the measurement target gas, at predetermined time intervals. Note that the pressure sensor 31 and the gas temperature sensor 32 may be _omitted when the pressure value _Ptotal and the gas temperature value T are known or when changes that affect the measurement are not assumed.

The laser control unit 50 includes a laser current control unit 51 that controls the laser current and a laser temperature adjustment unit 52 that controls the laser temperature.
The control unit 160 includes a CPU 161 and a memory 62. Further, the function processed by the CPU 161 will be described as a block. The water vapor amount calculation unit 61a that calculates the amount of water vapor in the measurement target gas is provided.

The laser beam intensity I (ν), pressure value P _total , and gas temperature value T are converted into digital values by the A / D converters 1, 2, and 3, respectively. By calculating I ₀ (ν) and I (ν) and applying the equation (1) to obtain the number density c, the amount of water vapor in the measurement target gas is calculated.

JP 2009-014585 A JP 2010-237075 A

However, in the gas analyzer 101 as described above, when the measurement target gas containing the amount of water vapor in the high humidity region flows in the sample flow path 70, dew condensation due to moisture condensation occurs on the incident optical window 71 or the emission optical window 71. It may occur in the optical window 72 or the like. When condensation occurs in this way, the laser light is scattered by condensation of moisture, so that a large change occurs in the intensity I (ν) of the laser light acquired by the photodiode, and water vapor in the measurement target gas The amount cannot be measured accurately. FIG. 8 is a graph showing an example of an absorption spectrum acquired when condensation occurs.
Therefore, in order to avoid condensation, it is conceivable to heat the sample flow path 70 through which the measurement target gas flows to a certain temperature or more. However, excessive heating changes the properties and state of the measurement target gas. There is a problem of letting it.

Therefore, the present applicant has studied a method for accurately measuring the amount of water vapor in the measurement target gas by determining that condensation has occurred in the incident optical window 71, the outgoing optical window 72, and the like. First, when a large change occurs in the intensity I ₀ (ν) of the laser beam having a non-absorption wavelength acquired by the photodiode, dew condensation occurs on the incident optical window 71, the outgoing optical window 72, and the like because there is no change in the amount of water vapor. It may have occurred. Therefore, the intensity I ₀ (ν) of the laser beam having the non-absorption wavelength stored in advance at a certain time t ₁ is compared with the intensity I ₀ (ν) of the laser beam having the non-absorption wavelength acquired at the current time t _2. By doing this, it is conceivable to determine that dew condensation has occurred by calculating the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light having the non-absorption wavelength. However, the cause of the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light exists in addition to dew condensation. For example, contamination of the incident optical window 71 and the outgoing optical window 72, degradation of the laser diode, deviation of the optical axis, and the like can be considered. That is, it is not possible to accurately determine the presence or absence of dew condensation only with the fluctuation amount ΔI ₀ (ν).

In order to accurately determine that the cause of the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light is dew condensation, it is necessary to distinguish it from other causes. Therefore, it was decided to determine whether or not condensation is possible. From the amount of water vapor in the measurement target gas, the _partial pressure value P _{partial of} water vapor is determined according to the following equation (2). If the _partial pressure value P _{partial of} water vapor is close to the saturated water vapor pressure at the temperature T at the current time t ₂ , is it possible for condensation to occur in the incident optical window 71 and the outgoing optical window 72? Can be determined.
P _partial = c × k × T (2)
Here, k is a Boltzmann constant.

Therefore, it has been found that when the intensity I (ν) of the measuring light changes greatly and the _partial pressure value P _partial is close to the saturated water vapor pressure, it is determined that condensation has occurred.

Further, instead of comparing the _partial pressure value Ppartial with the saturated water vapor pressure, the water vapor is expressed according to the following equations (3) and (4) derived from the SONNTAG (1990) equation known from the saturated water vapor pressure curve. in terms of partial pressure value P _partials dew point temperature T _d of essentially the same can be performed compared with the dew point temperature T _d and the gas temperature value T.
_{y = ln (P partial /611.213)} ··· (3)
When y ≧ 0 (when dew point temperature _Td is 0 ° C. or higher)
T _d = 13.715 × y + 8.4262 × 10−1 × y2 + 1.9048 × 10−2 × y3 + 7.8158 × 10−3 × y4
... (4)
In the above-described example, it is assumed that the dew point temperature T _d is from 0 to 100 ° C. However, even when the dew point temperature T _d is other than that, an approximate expression preferable for the saturated water vapor pressure curve is used. May be used.

That is, in the gas analyzer of the present invention, the measurement light in the sample channel in which the optical window is formed is passed through the optical window with measurement light having an absorption wavelength that is absorbed by water and a non-absorption wavelength that is not absorbed by water. Based on the light source unit that irradiates, the light receiving unit that receives the intensity of the measurement light that has passed through the measurement target gas through the optical window, the intensity of the measurement light of the absorption wavelength and the intensity of the measurement light of the non-absorption wavelength A gas analyzer including a water vapor amount calculation unit for calculating a water vapor amount in the measurement target gas, the intensity of the measurement light having a non-absorption wavelength stored in the first time, and after the first time Based on the amount of water vapor in the measurement target gas, by calculating the amount of fluctuation in the intensity of the non-absorption wavelength measurement light by comparing the intensity of the measurement light of the non-absorption wavelength acquired in the second time The partial pressure value of water vapor in the measurement target gas And comparing the partial pressure value with the saturated water vapor pressure to create a comparison result indicating the possibility of condensation, and the condensation on the optical window based on the comparison result and the fluctuation amount. A dew condensation determination unit that determines whether or not the optical window has occurred, a heater unit for heating the optical window, and a heater temperature control unit that controls the temperature of the heater unit , wherein the dew determination unit when it is determined that condensation on the window occurs, and the so that to send temporarily heating control command to the heater temperature control unit.

  As described above, according to the gas analyzer of the present invention, the amount of fluctuation in the intensity of the measurement light of the non-absorption wavelength is measured, and whether the condensation can occur because the partial pressure value and the saturated water vapor pressure are compared. Whether or not condensation has occurred in the optical window can be accurately determined from these two results.

(Means and effects for solving other problems)
In the above invention, as the optical window formed in the sample flow path, an incident optical window and an outgoing optical window facing the incident optical window are formed, and the light source unit includes The measurement light may enter the sample channel from the incident optical window, and the light receiving unit may receive the measurement light emitted from the output optical window to the outside of the sample channel.

  In the above invention, an optical window for input / output is formed as an optical window formed in the sample flow path, and a reflecting mirror facing the optical window for input / output is formed in the sample flow path. The light source unit causes measurement light to enter the sample channel from the incident / exit optical window, and the light receiving unit is reflected by the reflecting mirror and then flows from the incident / exit optical window. The measurement light emitted outside the road is received, and the dew condensation determination unit may determine whether or not dew condensation has occurred in the optical window or the reflecting mirror.

Furthermore, in the above invention, the heater unit for heating the optical window, the heater temperature control unit that controls the temperature of the heater unit, and the dew condensation determination unit determine that dew condensation has occurred in the optical window. In some cases, a heating control command is transmitted to the heater temperature control unit, so that when it is determined that condensation has occurred in the optical window or the reflecting mirror, the heater unit performs heating control to achieve a steady state. Therefore, the temperature can be temporarily raised to enable early recovery from the dew condensation state, and convenience can be improved.

The schematic block diagram which shows an example of the gas analyzer which is one Embodiment of this invention. The block diagram of the gas analyzer shown in FIG. The flowchart for demonstrating the determination method. The schematic block diagram which shows an example of the gas analyzer which is other embodiment of this invention. The schematic block diagram which shows an example of the gas analyzer using a wavelength-tunable semiconductor laser absorption spectroscopy. The block diagram of the gas analyzer shown in FIG. The graph which shows an example of the absorption spectrum acquired with the photodiode. The graph which shows an example of the absorption spectrum acquired when dew condensation arises.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and it goes without saying that various aspects are included without departing from the spirit of the present invention.

FIG. 1 is a schematic configuration diagram showing an example of a gas analyzer according to an embodiment of the present invention, and FIG. 2 is a block diagram of the gas analyzer shown in FIG. One direction horizontal to the ground is defined as an X direction, a direction horizontal to the ground and perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the X direction and the Y direction is defined as a Z direction. The same reference numerals are assigned to the same components as those of the conventional gas analyzer 101 described above.
The gas analyzer 1 includes a light source unit 10, a light receiving unit 20, a pressure sensor 31 that measures a pressure value _Ptotal , a gas temperature sensor 32 that measures a gas temperature value T, a heater unit 81, and a light source unit 10. The laser control part 50 to control, the heater temperature control part 80 which controls the temperature of the heater part 81, and the control part 60 comprised with a microcomputer or PC are provided.

  The heater unit 81 can heat the incident optical window 71 and the outgoing optical window 72, and is controlled by a control signal from the heater temperature control unit 80. In general, in order to prevent condensation, the incident optical window 71, the outgoing optical window 72, and the surrounding piping are generally heated. In the present invention, the heating is further temporarily performed. Therefore, the heater temperature adjustment control unit 80 operates in conjunction with the dew condensation determination unit 61d of the control unit 60. Specifically, the heater temperature control unit 80 receives a heating control command when it is determined by the dew condensation determination unit 61d described later that condensation has occurred. If the heating control command is continued from the measured absorption spectrum result until it is considered that the condensation has been completed after evaporating and drying, no more thermal load is applied to the measuring instrument and the sample gas.

The control unit 60 includes a CPU 61 and a memory 62. Further, the function processed by the CPU 61 will be described as a block. The water vapor amount calculation unit 61a that calculates the water vapor amount in the measurement target gas, and the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light in the non-absorption wavelength portion are calculated. A calculation unit 61b that performs the comparison, a comparison unit 61c that creates a comparison result indicating the possibility of condensation, and a condensation determination unit 61d that determines whether or not condensation has occurred in the incident optical window 71 and the emission optical window 72. Have Further, the memory 62 has a laser beam intensity storage area for storing the intensity I ₀ (ν) of the laser beam having a non-absorption wavelength.

Steam amount calculating unit 61a, the intensity of the laser beam I ([nu), and converted into a digital value by the pressure value _{P total,} respectively gas temperature value T A / D conversion unit 1, 2, 3, _{I 0} from the digital value By calculating (ν) and I (ν) and applying the equation (1) to obtain the number density c, control is performed to calculate the amount of water vapor in the measurement target gas. At this time, the water vapor amount calculation unit 61a stores the intensity I ₀ (ν) of the laser light having the non-absorption wavelength in the laser light intensity storage area.

The calculation unit 61b calculates the intensity I ₀ (ν) of the laser beam having the non-absorption wavelength stored at the first time t ₁ and the intensity of the laser beam having the non-absorption wavelength acquired at the current time (second time) t _2. Control for calculating the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light in the non-absorption wavelength portion is performed by comparing with I ₀ (ν).
For example, the intensity I ₀ (ν) of the laser beam having a non-absorption wavelength calculated from the spectrum waveform acquired at the current time t ₂ is obtained. Then, to obtain the intensity of the laser light non-absorbing wavelength obtained in the first hour t ₁ stored in the memory 62 I _{0 (ν).} Thus, the laser beam intensity I ₀ of the non-absorption wavelength, which is stored in the first hour t _{1 (ν),} the intensity I ₀ of the laser light non-absorbing wavelength acquired the current time t _{2 (ν)} By comparing, the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light in the non-absorption wavelength portion is calculated. As the intensity of the laser beam of the non-absorption wavelength, for example, the intensity may be measured at any point in the non-absorption wavelength band, and all integrated values and average values of the non-absorption wavelength band are taken. It doesn't matter.

Comparing unit 61c in accordance with equation (2) from the amount of water vapor in the measurement target gas with steam amount calculating unit 61a is acquired in the current time t _2, calculate the partial pressure value P _partials of water vapor in the gas to be measured, wherein (3), (4) to calculate the dew point temperature T _d according acquires the gas temperature values T acquired the current time t ₂ with steam amount calculation unit 61a, a dew point temperature T _d and the gas temperature value T By comparing these, control is performed to create a comparison result indicating the possibility of condensation.
For example, the dew point temperature _{T d} is T × 0.95 or higher (dew point temperature _{T d} is close to gas temperature value T) determines whether the. And if dew point temperature _Td is more than Tx0.95, the comparison result which shows that possibility that condensation will arise will be produced. On the other hand, if the dew point temperature _Td is less than T × 0.95, a comparison result indicating that the possibility of condensation is low is created.

The condensation determination unit 61d performs control to determine whether or not condensation has occurred in the incident optical window 71 and the emission optical window 72 based on the comparison result and the fluctuation amount ΔI ₀ (ν).
Here, a determination method for determining whether or not condensation has occurred in the incident optical window 71 and the outgoing optical window 72 will be described. FIG. 3 is a flowchart for explaining the determination method.
First, in the process of step S101, the water vapor amount calculation unit 61a converts the laser beam intensity I (ν), pressure value _Ptotal , and gas temperature value T into digital values by the A / D conversion units 1, 2, and 3, respectively. And get.

Next, in the process of step S102, the water vapor amount calculation unit 61a calculates I ₀ (ν) and I (ν) from the digital values and applies them to the equation (1) to obtain the number density c. The amount of water vapor in the target gas is calculated. At this time, the water vapor amount calculation unit 61a stores the intensity I ₀ (ν) of the laser light having the non-absorption wavelength acquired at the first time t ₁ in the laser light intensity storage area.
Further, the comparison unit 61c calculates the _partial pressure value Ppartial of water vapor in the measurement target gas according to the equation (2) from the water vapor amount in the measurement target gas calculated by the water vapor amount calculation unit 61a.

Next, in the process of step S103, the water vapor amount calculation unit 61a converts the laser beam intensity I (ν), the pressure value _Ptotal , and the gas temperature value T into digital values by the A / D conversion units 1, 2, and 3, respectively. Convert and get.
Next, in the process of step S104, the water vapor amount calculation unit 61a calculates I ₀ (ν) and I (ν) from the digital values and applies them to the equation (1) to obtain the number density c. The amount of water vapor in the target gas is calculated. At this time, the water vapor amount calculation unit 61a stores the intensity I ₀ (ν) of the laser light having the non-absorption wavelength acquired at the second time t ₂ in the laser light intensity storage area.
Further, the comparison unit 61c calculates the _partial pressure value Ppartial of water vapor in the measurement target gas according to the equation (2) from the water vapor amount in the measurement target gas calculated by the water vapor amount calculation unit 61a.

Next, in the process of step S105, the calculation unit 61b uses the intensity I ₀ (ν) of the laser light with the non-absorption wavelength stored at the first time t ₁ and the non-absorption wavelength acquired at the second time t _2. The amount of fluctuation ΔI ₀ (ν) of the intensity of the laser beam in the non-absorbing wavelength portion is calculated by comparing the intensity I ₀ (ν) of the laser beam. Then, the dew condensation determination unit 61d determines whether or not the fluctuation amount ΔI ₀ (ν) is, for example, 10% or more.
When the fluctuation amount ΔI ₀ (ν) of the intensity of the laser beam is less than 10%, in the process of step S106, the dew condensation determination unit 61d causes dew condensation on the incident optical window 71, the outgoing optical window 72, and the like. It is determined that there is no possibility that it has occurred, and the process returns to step S103. In addition, when a heating control command is transmitted to the heater temperature control unit 80 in the process of step S110 described later, it is considered that condensation has been completed after evaporation and drying, and a heating stop control command is transmitted to the heater temperature control unit 80. . Thus, by temporarily heating the incident optical window 71 and the outgoing optical window 72, it is possible to avoid applying a thermal load to the measuring instrument and the sample gas more than necessary.

On the other hand, when the fluctuation amount ΔI ₀ (ν) of the intensity of the laser beam is 10% or more, it is determined that there is a possibility that condensation has occurred in the incident optical window 71, the outgoing optical window 72, and the like. In the process of step S107, the comparison unit 61c obtains the _partial pressure value P _{partial of} water vapor calculated in the process of step S104, and calculates the dew point temperature _Td according to equations (3) and (4).
Next, in the process of step S108, the comparison unit 61c acquires the gas temperature value T calculated in the process of step S104, and determines whether or not the dew point temperature _Td is equal to or higher than T × 0.95. . When the dew point temperature _Td is less than T × 0.95, in the process of step S109, the comparison unit 61c creates a comparison result indicating that the possibility that condensation has occurred is low. Thereby, the dew condensation determination unit 61d determines that the cause of the fluctuation amount ΔI ₀ (ν) of the intensity of the laser light is other than dew condensation.

On the other hand, when the dew point temperature _Td is equal to or higher than T × 0.95, in the process of step S110, the comparison unit 61c creates a comparison result indicating that there is a high possibility that condensation will occur. The dew condensation determination unit 61d determines that dew condensation has occurred in the incident optical window 71 and the emission optical window 72, transmits a heating control command to the heater temperature control unit 80, and returns to the process of step S103. . Thus, by heating the incident optical window 71 and the outgoing optical window 72, water molecules attached to the incident optical window 71 and the outgoing optical window 72 are evaporated and dried.

As described above, according to the gas analyzer 1, the amount of fluctuation ΔI ₀ (ν) of the intensity of the laser beam having the non-absorption wavelength is measured, and the dew condensation is caused by comparing the _partial pressure value P _partial and the saturated water vapor pressure. It is also possible to determine whether or not condensation has occurred in the incident optical window 71 and the outgoing optical window 72 from the two results.

<Other embodiments>
In the gas analyzer 1 described above, the incident optical window 71 and the output optical window 72 are formed on the side wall of the sample flow path 70, but the input / output is formed on the side wall of the sample flow path 270. The optical window 271 may be formed and the reflecting mirror 272 facing the input / output optical window 271 may be formed in the sample channel 270.
FIG. 4 is a schematic configuration diagram showing an example of a gas analyzer 201 according to another embodiment of the present invention. The sample flow path 270 extends in the Z direction, and an input / output optical window 271 is formed on the side wall of the sample flow path 270, and the distance L in the X direction to the incident optical window 271 in the sample flow path 270. A reflecting mirror 272 is formed facing each other with a gap therebetween. The measurement target gas flows in the Z direction in the sample flow path 270.

The light source unit 10 is arranged so that laser light enters the sample channel 270 from the incident / exit optical window 271 in substantially the X direction, and the laser light is irradiated to the measurement target gas. Yes.
The light receiving unit 20 is a photodiode, and is disposed so as to receive laser light emitted from the incident / exit optical window 271 to the outside of the sample flow path 270 in the −X direction, and passes through the measurement target gas. The intensity I (ν) is received.

As a result, the laser light traveling in the X direction passes through the incident / exit optical window 271 to be irradiated onto the measurement target gas, changes the traveling direction by the reflecting mirror 272, travels in the −X direction, and enters / exits. The light passes through the optical window 271 and enters the photodiode.
As a result, the dew condensation determination unit 61d performs control to determine whether or not dew condensation has occurred in the incident / exit optical window 271 and the reflecting mirror 272 based on the comparison result and the fluctuation amount ΔI ₀ (ν).

  The present invention can be used in a gas analyzer or the like that measures the amount of water vapor in a gas using laser absorption spectroscopy.

DESCRIPTION OF SYMBOLS 1 Gas analyzer 10 Light source part 20 Light receiving part 61a Water vapor | steam amount calculating part 61b Calculation part 61c Comparison part 61d Condensation determination part 70 Sample flow path 71 Incident optical window 72 Outgoing optical window

Claims (3)

A light source unit that irradiates the measurement target gas in the sample channel in which the optical window is formed, through the optical window with measurement light having an absorption wavelength absorbed by water and a non-absorption wavelength not absorbed by water;
A light receiving unit that receives the intensity of the measurement light that has passed through the measurement target gas through an optical window;
A gas analyzer comprising a water vapor amount calculation unit that calculates the amount of water vapor in the measurement target gas based on the intensity of measurement light having an absorption wavelength and the intensity of measurement light having a non-absorption wavelength,
By comparing the intensity of the measurement light of the non-absorption wavelength stored in the first time with the intensity of the measurement light of the non-absorption wavelength acquired in the second time after the first time, A calculation unit for calculating the fluctuation amount of the intensity of the measurement light;
Comparison indicating the possibility of condensation by calculating the partial pressure value of water vapor in the measurement target gas based on the amount of water vapor in the measurement target gas and comparing the partial pressure value with the saturated water vapor pressure A comparison unit that creates the results;
Based on the comparison result and the fluctuation amount, a dew condensation determination unit that determines whether or not dew condensation has occurred in the optical window ;
A heater unit for heating the optical window;
A heater temperature control unit for controlling the temperature of the heater unit ,
The condensation determination unit, when it is determined that dew condensation occurs in the optical window, the gas analyzer apparatus characterized that you send a temporary heating control command to the heater temperature control unit. As the optical window formed in the sample flow path, an incident optical window and an emission optical window facing the incident optical window are formed,
The light source unit causes measurement light to enter the sample channel from the incident optical window, and the light receiving unit receives measurement light emitted from the output optical window to the outside of the sample channel. The gas analyzer according to claim 1. As the optical window formed in the sample flow path, an input / output optical window is formed, and a reflecting mirror facing the input / output optical window is formed in the sample flow path,
The light source unit causes measurement light to enter the sample channel from the incident / exit optical window, and the light receiving unit is reflected by the reflecting mirror, and then is reflected from the incident / exit optical window to the outside of the sample channel. Receives the emitted measurement light,
The gas analyzer according to claim 1, wherein the dew condensation determination unit determines whether dew condensation has occurred in the optical window or the reflecting mirror.

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