JP5022334B2 - Gas component measuring device and optical axis adjusting method thereof - Google Patents

Description

  The present invention relates to a gas component measuring device that measures a gas component concentration in a gas to be measured such as exhaust gas, and an optical axis adjusting method thereof.

  Conventionally, it is known that the concentration of a gas component in fuel gas is measured by a laser device (see Patent Document 1).

JP 2005-24249 A

By the way, the laser device is required to perform continuous measurement over a long period of time, and extending its life is a problem.
In particular, there is a problem of a decrease in the emission efficiency of Raman scattered light due to a decrease in laser output or an optical axis shift.
Therefore, the advent of a gas component measuring apparatus that can stably measure over a long period of time is eagerly desired.

  In particular, mechanical effects such as vibration are a major factor in laser devices. When installed near industrial equipment and directly measuring exhaust gas, etc., it is necessary to adjust the optical axis. Optical axis measures are desired.

  In view of the above problems, the present invention constantly monitors the decrease in the emission efficiency of Raman scattered light due to the decrease in the laser output and the deviation of the optical axis, adjusts as necessary, and is stable over a long period of time. It is an object of the present invention to provide a gas component measuring apparatus capable of measuring a gas component and an optical axis adjusting method thereof.

  A first aspect of the present invention for solving the above-described problem is a gas component measuring apparatus for measuring a gas component concentration in a measurement gas from Raman scattering generated by laser light irradiated to the measurement gas. A laser device for irradiating the measurement gas with laser light, a spectroscopic unit for measuring Raman scattered light generated by the laser light irradiated in the measurement region where the measurement gas is introduced, and A gas component measuring apparatus comprising: a probe that is temporarily inserted to generate or reflect light other than Raman scattered light; and a photodetector that detects light other than Raman scattered light. .

  According to a second aspect of the present invention, there is provided the gas component according to the first aspect, wherein when the laser beam is not in the measurement region, the adjustment of the reflection mirror optical axis of the laser beam of the laser device or the position of the condenser lens is performed. In the measuring device.

  According to a third aspect of the present invention, there is provided the gas component measuring apparatus according to the first or second aspect of the invention, wherein the laser output measuring unit includes a position detecting means.

  According to a fourth aspect of the present invention, there is provided the gas component measuring device according to any one of the first to third aspects, further comprising a laser output measuring unit, wherein the laser beam output of the laser device is corrected.

  According to a fifth aspect of the present invention, if any one of the first to fourth gas component measuring devices is used, a probe is inserted into the measurement region, and the laser beam is present within the range of the laser beam diameter, it is determined as normal. The measurement is continued as it is, and when the laser beam deviates outside the range of the measurement region, the output of the laser beam of the laser device is corrected, and the optical axis adjustment method of the gas component measuring device is provided.

  According to the present invention, a probe (for example, a needle) that generates or reflects light other than Raman scattered light and a photodetector that detects light other than Raman scattered light are provided. It can always be monitored that laser light is reliably present in the region.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A gas component measuring apparatus for measuring a composition in fuel gas according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a gas component measuring apparatus according to an embodiment.
As shown in FIG. 1, the gas component measuring device 10 is a gas component measuring device that measures the gas component concentration in the measured gas 12 from Raman scattering generated by the laser light 11 irradiated to the measured gas 12. A laser device 13 for irradiating the measurement gas 12 with a laser beam 11 and a spectroscopic unit for measuring Raman scattered light 15 generated by the laser beam 11 irradiated in the measurement region 14 into which the measurement gas 12 is introduced 16 and a probe that is temporarily inserted into the measurement region 14 and generates light 17 other than Raman scattered light (see FIG. 2; for example, fluorescence, plasma light, etc.) or reflects (for example, multiple reflection of laser light). A needle 18 and a light detector 19 for detecting light 17 other than the Raman scattered light are provided, and light 17 other than the Raman scattered light by the temporarily inserted needle 18. The information, the optical axis adjustment of the laser beam 11, and performs one or both of the focusing position of the spectroscopic unit.
Here, in FIG. 1, reference numeral 20 denotes a measurement chamber in which a measurement gas 12 is introduced and irradiates a laser beam 11 to measure a gas component, 21 denotes a reflection mirror that reflects the laser beam 11 from the laser device 13, and 22. Is a condensing lens for condensing the laser beam 11, 23 is an ICCD (Intensified Charge Coupled Device) camera, and 24 is a data processing means (CPU).

Here, the needle 18 which is a probe for generating (for example, fluorescence, plasma light, etc.) or reflecting (for example, multiple reflection of laser light) other than the Raman scattered light is made of, for example, stainless steel, iron, It is preferable to generate plasma light in which components such as nickel and chromium are combined.
Alternatively, fluorescence may be generated by applying or continuously supplying a fluorescent agent to the surface of the needle 18.

As shown in FIG. 2, plasma light 17 generated by inserting the needle 18 is detected by a photodetector 19, and examples of the detector include a photomultiplier tube and a photodiode.
The plasma light 17 has a high laser light, but the multiple reflection has a low laser light density. Therefore, the sensitivity of the photodetector 19 is adjusted according to the measurement target.
Then, as will be described later, it is possible to determine whether or not the laser beam 11 is correctly irradiated into the measurement region 14 by inserting the needle 18. Therefore, by performing this monitoring every predetermined period, the deviation of the optical axis of the laser beam 11 is monitored, and if the optical axis of the laser beam is deviated, the optical axis is adjusted. By doing so, it becomes possible to continuously and stably measure gas components over a long period of time.

Here, the laser beam 11 from the laser device 13 is reflected to the measurement chamber 20 side via the reflection mirror 21, condensed by the condenser lens 22 that is a condenser, and then sent into the measurement chamber 20. The laser beam 11 is incident on the measurement region 14 and irradiates the measurement gas 12 introduced into the measurement chamber 20.
Note that the measurement chamber 20 has a function of introducing, holding, or discharging the gas 12 to be measured inside, and this introduction causes a part of the supply pipe for sending the product gas to be branched or branched from the supply pipe. May be introduced.

Further, the Raman scattered light 15 scattered from the center of the measurement region 14 is spectrally separated by the spectroscopic unit 16 via an optical group (not shown) such as a polarizer, a condenser lens, and a filter, for example, and the spectroscopic unit 16 The intensity of light of each wavelength is measured by the ICCD camera 23 connected to the.
The measurement data from the ICCD camera 23 is sent to the CPU 24, where it is extracted as, for example, gas component measurement data.

In the present embodiment, the gas to be measured 12 may be any exhaust gas discharged from industrial equipment.
As an example, an example of a measurement chart of biomass gasification gas is shown in FIG. As shown in FIG. 3, hydrogen (H ₂ ) is 8%, water (H ₂ O) is 62%, carbon dioxide (CO ₂ ) is 12%, carbon monoxide (CO) is 6%, methane (CH ₄ ) Is 1%, and nitrogen (N ₂ ) is 12%. The ratio is calculated from the chart.

Below, each structural member of the gas component measuring device 10 using a laser apparatus is demonstrated.
First, the laser device 13 having a function of outputting the laser beam 11 and irradiating the measurement gas 12 will be described.
The laser device 13 outputs laser light 11 by laser oscillation, and the desired wavelength of the laser light 11 can be used depending on the laser used.
In the present invention, it is preferable to use one having a wavelength of visible light (400 nm to 700 nm). Here, the one of 532 nm is used.

Note that the power meter 26 provided in the measurement chamber 20 is provided in the traveling direction of the laser beam 11 output from the laser device 13 and is a computing device that can accurately measure the output of the laser beam 11. is there. This numerical value is fed back to adjust the output of the laser device 13.
Instead of the power meter, a laser beam profiler may be installed to detect the deviation of the optical axis of the laser beam.
Thereby, the position detection accuracy of the laser beam is improved, and the optical axis can be corrected quickly. However, it is not suitable for poor environments.

  The reflection mirror 21 is a mirror that reflects the traveling direction of the output laser beam 11 toward the measurement chamber 20 where the measurement target gas 12 exists by reflection. By adjusting the angle of the mirror 21, measurement at an arbitrary position in the measurement region 14 is possible.

  Next, a description will be given of the measurement chamber 20 having a function of holding or circulating the measurement gas 12 in such a manner that the laser beam 11 can be irradiated. The measurement chamber 20 has a structure in which the measured gas 12 to be measured is present inside and does not leak to the outside (including the laser unit and the spectroscope). Note that the measurement laser beam 11 and the Raman scattered light 15 from the measured gas 12 enter and exit from the first window 27-1 and the second window 27-2.

  The second window 27-2 is a quartz glass window for preventing the measured gas 12 from flowing out. The reason why it is made of quartz glass is to allow the laser beam 11 to pass through the window. This window is doubled so that gas does not leak even if one piece of quartz glass is broken.

  Further, an electromagnetic valve (not shown) is provided in the passage of the laser beam 11 in the measurement chamber 20 and is normally closed. This is because if the second window 27-2 on the measurement chamber 20 side is exposed to the gas 12 to be measured for a long period of time, the second window 27-2 is caused by impurities in the gas 12 to be measured. This is because it becomes dirty and measurement with a laser becomes difficult due to the contamination. The solenoid valve is opened during measurement.

  The measurement chamber 20 is a place including the measurement region 14 where the measurement gas 12 in the traveling direction of the laser beam 11 exists, and the measurement target gas 12 existing in the measurement region 14 is irradiated with the laser beam 11. The measurement is made. However, the gas to be measured 12 does not need to stay in this place, and is in the middle of the gas supply pipe, and the gas is flowing (moving) in the pipe without stagnation. Can be measured.

  Next, the spectroscopic unit 16 having a function of separating the Raman scattered light 15 from the measured gas 12 and taking it out as measurement data will be described. Here, the Raman scattered light 15 scattered from the central portion of the measurement region 14 forms an angle from the laser light 11 and passes through the second window 27-2 and the first window 27-1, and the spectroscopic unit. Enter 16.

  The polarizer (not shown) provided in the spectroscopic unit 16 is a polarizing means that transmits only the scattered light having a specific polarization plane without changing the traveling direction. The scattered light transmitted by the polarizer is After being condensed by a condenser lens (not shown), only scattered light having a specific wavelength is transmitted by a filter (not shown). In this embodiment, a filter that transmits light in a region of 570 to 700 nm is used.

  And the Raman scattered light 15 which became a specific wavelength area | region is spectral-divided by the spectroscopy part 16, and the intensity | strength of light is measured with the ICCD camera 23 connected here. The ICCD camera 23 is a photomultiplier type device that measures the intensity of light of each wavelength separated by the spectroscopic unit 16.

FIG. 4 illustrates a method for adjusting the deviation of the optical axis of the laser beam by the gas component measuring device 10, and is a schematic diagram in which the laser device 13, the ICCD camera 23, and the needle 18 are synchronized.
First, three timing signals are output from the synchronizer. When these signals are expressed as signals 1 to 3, signal 1 is a signal for controlling the oscillation timing from the laser device 13, signal 2 is a signal for controlling the imaging timing from the ICCD camera 23, and signal 3 is a needle. 18 is a signal for controlling the operation of 18.
First, signals 1 and 2 are output from the synchronization device and input to the laser device 13 and the ICCD camera 23, respectively.
The laser device 13 performs laser oscillation after the signal 1 is input (the delay time until the laser oscillation is performed after the signal 1 is input is not considered because the delay time is as short as nanoseconds).
For example, if the signal 1 oscillated from the synchronization device is 10 Hz, laser oscillation is oscillated at a cycle of 10 times per second. After the laser oscillation, the Raman scattered light 15 of the fuel gas component reaches the ICCD camera 23 in nanosecond order, so the shutter of the ICCD camera 23 is opened.
At this time, in this example, for example, nine times are used for detecting the Raman scattered light 15 of the gas to be measured, and the remaining one time is used for needle insertion.
The needle insertion time at this time is less than 100 ms.
Light (plasma light or the like) generated by the inserted needle 18 is detected by a photodetector 19.
Thereby, the position of the laser beam 11 in the measurement region 14 of the Raman scattered light 15 can be confirmed online.

Next, needle insertion and optical axis adjustment will be described with reference to FIGS.
FIG. 5 is a flowchart of the monitoring and adjustment.
As shown in FIGS. 2 and 5, the needle 18 is inserted into the measurement region 14 (S11).
Next, the plasma light 17 is detected by the photodetector 19, and it is determined whether there is no deviation of the optical axis of the laser beam 11 (normal) or there is a deviation of the optical axis (abnormal) (S12).
If there is no optical axis deviation (normal), continue measurement.
On the other hand, if there is a deviation of the optical axis (abnormal), the optical axis adjustment of the laser light (reflection mirror 21 and condenser lens 22) is performed (S13).
The needle insertion operation is performed again, and the optical axis is adjusted until the deviation of the optical axis is allowed.

Here, a method for determining the presence or absence of optical axis deviation will be described with reference to FIG.
As shown in FIG. 6, it is a schematic diagram showing how the needle 18 is inserted into the measurement region 14. In FIG. 1, the needle 18 is illustrated. However, this is for explaining the configuration, and the actual insertion is performed when the direction perpendicular to the paper surface in FIG. The insertion is made from the vertical direction perpendicular to the axis (from the top to the bottom in the drawing).
Therefore, if the laser beam is within the range of the diameter (approximately 3 mm) of the laser beam, it is determined as a normal case.
When the laser beam is shifted to the upper side ([1] direction) of the measurement region, the output is increased. On the other hand, when the laser beam is shifted to the lower side and the left and right sides ([2] to [4] directions) of the measurement region, the output is reduced.

Therefore, when it is determined that the output is within a predetermined range (for example, output 100 ± 10%), the optical axis is not adjusted and the gas component is measured by switching to the measurement mode.
On the other hand, when it is determined that the output exceeds the predetermined range (for example, the output is 100 ± 10 or more), the optical axis is adjusted. The optical axis adjustment mode is continued, and after confirming that the optical axis adjustment mode is within a predetermined range, the measurement mode is switched to measure the gas component.

  This measurement mode may be performed 2-3 times a day or several times a day, but when it is determined that optical axis adjustment is frequently required, such as when the installation environment of the laser device is poor. The number of times may be further increased.

FIG. 7 is a diagram showing the correlation between the Raman scattering signal intensity by the laser beam and the laser output, and it can be confirmed that the Raman scattering decreases in proportion to the decrease in the laser output.
Therefore, the appropriate Raman scattering signal intensity is always measured by checking the optical axis adjustment of the laser device described above and confirming whether or not the laser output has decreased.
Here, adjustment of the output of the laser device can be handled by correcting the voltage value or the current value. Examples of the case of controlling by voltage include a flash lamp excitation type laser device, and examples of cases of controlling by current include a laser diode excitation type laser device.

The gas component measuring apparatus according to the present invention measures the composition of a product gas from, for example, a pressurized fluidized bed boiler, a gasification furnace, a coke oven, etc. When the phase component concentration is measured, the gas component measurement can be stably performed over a long period of time by constantly monitoring the optical axis of the laser beam.
Moreover, the gaseous-phase component density | concentration of the useful gas (for example, GTL) obtained from not only a power plant but a chemical plant can be measured.

  As described above, according to the gas component measuring apparatus of the present invention, the gas component can be stably measured over such a long period, and various gas phase component concentrations can be stably measured.

It is the schematic of the gas component measuring device which concerns on an Example. It is the schematic of the gas component measuring device which concerns on an Example. It is a measurement chart of biomass gasification gas. It is a schematic diagram which synchronizes a laser apparatus, an ICCD camera, and a needle. It is a flowchart of monitoring and adjustment. It is explanatory drawing of the method of judgment of the presence or absence of the deviation | shift of an optical axis. FIG. 6 is a correlation diagram between Raman scattering signal intensity and laser output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas component measuring device 11 Laser beam 12 Gas to be measured 13 Laser device 14 Measurement area 15 Raman scattered light 16 Spectrometer 17 Light other than Raman scattered light 18 Needle 19 Photo detector

Claims (5)

In the gas component measuring device that measures the gas component concentration in the gas to be measured from the Raman scattering generated by the laser light irradiated to the gas to be measured,
A laser device for irradiating the measurement gas with laser light;
A spectroscopic unit for measuring Raman scattered light generated by laser light irradiated in the measurement region into which the measurement gas is introduced;
A probe that is temporarily inserted into the measurement region and generates or reflects light other than Raman scattered light;
A gas component measuring apparatus comprising a photodetector for detecting light other than the Raman scattered light. In claim 1,
A gas component measuring apparatus that performs adjustment of an optical axis of a reflection mirror of a laser beam of a laser apparatus or adjustment of a position of a condensing lens when the laser beam is not within a measurement region. In claim 1 or 2,
A gas component measuring apparatus comprising a position detection means in a laser output measuring section. In any one of Claims 1 thru | or 3,
It has a laser output measurement unit,
A gas component measuring device for correcting the output of laser light from a laser device. Using the gas component measuring device according to any one of claims 1 to 4,
Insert the probe into the measurement area,
If the laser beam exists within the range of the laser beam diameter, it is determined to be normal,
Continue measuring,
A method of adjusting an optical axis of a gas component measuring device, comprising: correcting a laser beam output of a laser device when the laser beam deviates outside a measurement region.

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