JP6000180B2 - Laser measurement method - Google Patents

Description

  The present invention relates to a laser measuring device.

  Conventionally, for example, as a method for measuring the gas concentration in a gas pipe in a boiler plant, a method based on a semiconductor laser absorption method has been established and JISized (JISB 7993: Non-Patent Document 1).

In this laser device using the semiconductor laser absorption method, a laser beam is irradiated from a laser device to a sample pipe that introduces a gas branched from a gas pipe (main flue), and a gas to be measured (for example, ammonia) The components / concentration etc. are analyzed.
For example, in the first detector, the reference light (I ₀ ) is obtained, and in the second detector, the intensity (I) of the transmitted light in the sample pipe is obtained, and the transmittance T = (I / I ₀ ) is obtained. This analysis method enables online analysis of various gas component concentrations.

JISB7993

  By the way, since the laser means uses a laser oscillation unit and a laser light receiving unit, when introducing laser light into a measurement field, a quartz window for introducing and deriving a laser such as quartz is used.

  Moreover, since the gas environment of the boiler plant to be measured is inferior due to the presence of dust or the like, purge means for blowing, for example, nitrogen gas from the inside of the quartz window is installed. However, this purging means has a problem that a large-scale compressor or the like is further required in a place where a lot of soot accumulates, and if the number of measurement places increases, a secondary cost associated with the measurement increases. is there.

In view of the above problems, an object of the present invention is to provide a laser measuring apparatus and a laser measuring method capable of introducing and deriving a laser without using a purge means.

A first invention of the present invention for solving the above-described problem is a laser introducing means for introducing laser light from a laser beam running section into a measurement field, and a laser receiving section for introducing the introduced laser light from the measurement field. A laser lead-out means for leading to the side, wherein the measurement field has a negative pressure, and the laser introduction means and the laser lead-out means transmit a laser beam through which the laser light is transmitted, and the laser light A laser measurement method using a laser measurement device having a window frame that supports a transmission window and an attachment flange that attaches the window frame to a wall surface of the measurement field with a gap of a predetermined interval. In the laser measurement method, the method includes a step of removing the soot by increasing the inflow amount of outside air by setting the interval of the gap of the window frame larger than the predetermined interval when the soot is accumulated.

  According to the present invention, by providing a gap between the window frame and the mounting flange, outside air flows into the negative pressure measurement field from the outside through the gap. As a result, the outside air forms an inflow flow that passes through the gap, and the inflow flow prevents the exhaust gas from flowing into the inner surface side of the quartz window, thereby eliminating the occurrence of contamination on the inner surface of the quartz window. .

FIG. 1 is a schematic diagram of a laser measurement apparatus according to the first embodiment. FIG. 2 is a schematic diagram of a laser measurement apparatus according to the second embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

FIG. 1 is a schematic diagram of a laser measurement apparatus according to the first embodiment.
As shown in FIG. 1, a laser measuring apparatus 10A according to the present embodiment includes a laser introducing means 14 for introducing a laser beam 12 from a laser traveling light section 11 into a flue 13 as a measurement field, and an introduced laser beam 12 And a laser deriving means 16 for deriving the light from the flue 13 to the laser light receiving unit 15 side. The inside of the flue 13 has a negative pressure, and the laser introducing means 14 and the laser deriving means 16 are provided with the laser beam 12. A quartz window 21 that is a laser beam transmitting window, a window frame 22 that supports the quartz window 21, and a window frame 22 that is attached to a wall surface of a flue 13 that is a measurement site with a gap 23 at a predetermined interval. It has the attachment flange 24 attached using the volt | bolt 25 which is a means.

By providing the gap 23 between the window frame 22 and the mounting flange 24, the inside of the flue 13 is in a negative pressure state, so the outside air 26 flows into the flue 13 from the outside.
As a result, the outside air 26 forms an inflow flow that passes through the gap 23.
This inflow flow prevents the exhaust gas 19 from flowing into the inner surface side of the quartz window 21, and as a result, the occurrence of contamination on the inner surface of the quartz window 21 is eliminated.

  Here, when the internal pressure in the flue 13 is a negative pressure (for example, 200 mmAq), the flow rate of outside air passing through the gap 23 is about 5 to 30 m / s (preferably 10 to 15 m / s). Moreover, it is preferable to set it as about 50-500 mmAq as a range of the negative pressure in the flue 13 which is a measurement field.

  As a result, according to the present invention, window contamination of the quartz window 21 is prevented. Conventionally, it has been necessary to install a gas purging means having a large compressor or the like in order to perform a large amount of nitrogen purging in order to prevent window contamination, but this installation can be omitted and the measurement cost can be reduced. be able to.

  In addition, in the measurement over a long period of time, even when nitrogen purging by the purging means is performed, the transmittance of the window is reduced due to the adhesion of fine dust, but according to the present invention, this decrease in the transmittance is also prevented. be able to.

Here, the adjustment of the inflow amount of the outside air 26 can be changed as appropriate by adjusting the gap 23.
For example, when the gap 23 is increased, the inflow amount of the outside air 26 is increased. On the other hand, when the gap 23 is made smaller, the inflow amount of the outside air 26 becomes smaller.
In particular, when dust accumulates on the corner portion 22a of the window frame 22 inside the quartz window 21, the gap 23 is increased to increase the inflow amount of the outside air 26 so as to remove the accumulated dust. It may be.

  The installation of the laser measuring device 10A of the present invention can be applied to laser measurement when measuring leaked ammonia, for example, on the downstream side of the flue of the denitration device. It can be applied to general laser measurement of gas components.

Here, in laser measurement, for example, in order to measure ammonia (NH ₃ ) concentration, a semiconductor laser (semiconductor element: InGaAs can be exemplified. Wavelength: 1.5 μm, output: about 1 mW is exemplified. Can be used).
Further, when measuring nitrogen oxide (NOx), a quantum cascade laser (semiconductor element: InGaAs / InAlAs can be exemplified. Wavelength: 5 to 6 μm, output: about 1 mW can be exemplified. .) Can be used.

Moreover, as a gas component other than ammonia, when measuring the SO ₂ (sulfur dioxide) is a quantum cascade laser: can be used (wavelength 7.0~7.5μm can be exemplified.). Further, when methane (CH ₄ ) is measured as a gas component, a semiconductor laser (semiconductor element: InGaAs can be exemplified. Wavelength: 1.6 μm, output: about 1 mW can be exemplified. .) Can be used.

  Further, although the measurement is performed in the infrared spectral region, the present invention is not limited to this, and can be applied to the spectral measurement in the visible / ultraviolet region.

FIG. 2 is a schematic diagram of a laser measurement apparatus according to the second embodiment. The same members as those of the laser measuring apparatus according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIG. 2, the laser measurement apparatus 10B according to the present embodiment further covers the laser introduction means 14 and the laser lead-out means 16 in the laser measurement apparatus 10A according to the first embodiment shown in FIG. A cover 32 having a filter 31 is partially installed. In the figure, reference numeral 33 denotes a fixing bolt for fixing the cover 32.

  Since the cover 32 is installed and the outside air 26 is introduced through the filter 31 provided in a part of the cover 32, the dirt of the outside air 26 can be removed and the clean outside air 26 can be introduced into the flue 13. .

  Further, a plurality of laser introducing means 14 may be covered with one cover 32.

DESCRIPTION OF SYMBOLS 10A, 10B Laser measuring device 11 Laser running part 12 Laser light 13 Flue 14 Laser introduction means 15 Laser light receiving part 16 Laser extraction means 21 Quartz window 22 Window frame 23 Gap 24 Mounting flange

Claims (1)

Laser introducing means for introducing laser light from the laser transmitting section into the measurement field;
A laser deriving unit for deriving the introduced laser beam from the measurement field to the laser light receiving unit side;
The inside of the measurement field is negative pressure,
The laser introducing means and the laser derivation means are
A laser light transmission window that transmits the laser light;
A window frame that supports the laser light transmitting window;
A laser measurement method using a laser measurement device having a mounting flange for attaching the window frame to a wall surface of the measurement field with a gap of a predetermined interval,
And a step of removing the dust by increasing the inflow amount of outside air by setting the gap interval of the window frame larger than the predetermined interval when the dust is accumulated on the window frame. Method.

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