JP7229523B2 - laser gas analyzer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laser type gas analyzer, and more particularly to a laser type gas analyzer that prevents dust from accumulating inside a mounting flange.

FIG. 5 shows an example in which the laser gas analyzer is applied to the flue (space to be measured), and FIG. 6 shows the light emission side as a three-dimensional view. is more schematically represented.

Laser light emitted from the light emitting unit 100 is emitted to the flue 30, which is the space to be measured, through the light emitting window 110, and the laser light that has passed through the flue 30 is received by the light receiving unit 200 through the light receiving window 210. be. Here, the light emitting portion 100, the light receiving portion 200, and the flue 30, which is the space to be measured, are separated by the light emitting window 110 and the light receiving window 210, respectively.

A mounting flange 41 a is provided on the flue 30 side of the light emitting window 110 of the light emitting section 100 , and a purge gas connection port 131 to be described later is provided between the mounting flange 41 a and the light emitting window 110 . On the other hand, a riser pipe 42 having a predetermined height communicates with the flue 30, and a fixed flange 41b corresponding to the mounting flange 41a is provided at the tip of the riser pipe 42 to constitute the installation table 40. ing. The mounting flange 41a is fixed to the fixing flange 41b, whereby the light emitting part 100 is fixed to the mounting base 40 of the flue 30. As shown in FIG.

With the light emitting unit 100 attached to the flue 30 as described above, a separately prepared purge gas tank is connected to the purge gas connection port 131, and the riser pipe 42 is supplied with a purge gas of about 50 to 100 L/min at all times. to keep the window 110 of the light emitting section 100 clean. This structure is also provided on the measurement target space side of the window 210 of the light receiving unit 200, and the window 210 of the light receiving unit 200 is also kept clean.

US Patent No. 9244003

As described above, by constantly flowing a purge gas of about 50 to 100 L/min to the measurement object space side of the light emitting window 110 and the measurement object space side of the light receiving window 210, adhesion of dust to the light emitting window 110 and the light receiving window 210 is prevented. This reduces the intensity of the received light.

However, when there are various types of incinerated materials, such as municipal waste incineration facilities, the flue contains highly adsorbable coexisting gases, moisture, dust, etc., in addition to the gas to be measured. For this reason, depending on the flow velocity in the flue, dust accumulates inside the riser pipe 42 of the installation table 40, which serves as the optical path, and the optical path pipe is blocked. A decrease in intensity will cause a decrease in the signal-to-noise ratio in the measurements.

The method of flowing purge gas is effective for short-time operation of the process, but it is not sufficient for long-time operation because dust accumulates in the vicinity of the riser pipe 42 and clogs it. is the current situation.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned conventional circumstances, and provides a laser type gas analyzer that can secure an optical path even if it is used for a long time.

The present invention relates to a laser type gas analyzer comprising a light emitting part that emits a laser that irradiates a measurement space through a light emitting window, and a light receiving part that receives the laser that has passed through the measurement target space through a light receiving window, It consists of the following high-pressure tank, optical path tube, blast tube, solenoid valve, and open/close control unit.

The high-pressure tank is filled with blast gas, and an optical path tube is inserted between the light-emitting window or the light-receiving window and the space to be measured. Further, the tip of the blast tube (on the side of the space to be measured) communicates with the optical path tube, and the rear end of the blast tube is provided with a connection port through which the high-pressure tank can be attached and detached. A solenoid valve is provided between the connection port and the blast pipe, and an opening/closing control unit for controlling opening/closing of the solenoid valve is further provided.

The opening/closing control unit is provided with a timer that opens the electromagnetic valve for a predetermined period of time at predetermined intervals, and a calculation unit that calculates the transmittance of the laser from the light emitting unit to the light receiving unit. , open for a predetermined time according to the transmittance.

With the above configuration, the blast gas can be jetted into the riser pipe of the installation table as needed, so that the adhering dust can be efficiently blown off, and the apparatus can be used for a long period of time. In particular, it is effective to use both control of the electromagnetic valve based on the transmittance of the optical path tube and control of the electromagnetic valve based on the timer.

1 is a perspective view of the entire invention; FIG. 1 is an exploded perspective view of the present invention; FIG. Fig. 3 is a block diagram showing a control unit of the present invention; It is a figure explaining the blast control by this invention. It is a conceptual diagram of a conventional laser type gas analyzer. FIG. 6 is a three-dimensional view showing the light emitting side of FIG. 5;

FIG. 1 is a perspective view of the entire invention, and FIG. 2 is an exploded perspective view thereof. Since the light-emitting side and the light-receiving side have symmetrical structures, FIGS. 1 and 2 show only the structure on the light-emitting side.

As described above, the mounting flange 41a is provided on the flue 30 side of the light emitting window 110 of the light emitting part 100, and the rear end of the riser pipe 42 of the flue 30 is provided with a fixing flange 41b corresponding to the mounting flange 41a. is provided.

On the other hand, the blaster unit 300 has the following configuration.

A flange 51a matching the mounting flange 41a is provided at the rear end (light emitting section side, light receiving section side) of the optical path tube 50 having a predetermined length, and a flange matching the fixing flange 41b is provided at the tip (flue side). 51b is provided. The tip of a blast tube 52 communicating with the optical path tube 50 forms an acute angle with respect to the axial direction of the optical path tube 50 and communicates with the flange 51b side. The connection port 55 of the compression tank 60 is provided through the .

The blaster unit 300 configured as described above is inserted between the mounting flange 41a and the fixed flange 41b of the installation base 40, and the mounting flange 41a and the flange 51a, and the fixed flange 41b and the flange 51b are fixed. As a result, the blaster unit 300 is fixed between the light emitting unit 100 (light receiving unit 200) and the installation base 40 of the flue 30. Further, the connection port 55 is provided with a compression tank of nitrogen gas or instrument air. 60 is connected.

With the above configuration, by opening the electromagnetic valve 54, dust accumulated in the vicinity of the opening of the optical path tube 50 to the flue 30 can be blown off.

FIG. 3 is a block diagram showing a control circuit for controlling the opening and closing of the electromagnetic valve 54. As shown in FIG.

A driving current obtained by superimposing a sawtooth wave of several tens to several hundred Hz with a sine wave of several tens to hundreds of kHz is applied to the light emitting module 142 from the light emission control unit 141 of the light emitting unit 100, and the wavelength variable laser is emitted from the light emitting window 110. Illuminated. After passing through the measurement target space (the flue 30 ), the laser is received by the light receiving module 242 of the light receiving unit 200 , photoelectrically converted, and input to the calculation unit 241 . The calculation unit 241 mainly calculates the concentration of the gas to be measured in the space to be measured. Then, the intensity of the light received by the light receiving module 242 (light receiving intensity/light emitting intensity) is also calculated.

The ratio of the received light intensity to the emitted light intensity obtained in this way is input to the blast control unit 243. Here, when the received light intensity/light emitted intensity is equal to or less than a predetermined threshold value (for example, 10%), the blast control The part 243 opens the electromagnetic valves 54 on the light emitting side and the light receiving side for a predetermined time. As a result, the opening/closing control of the electromagnetic valve 54 can be performed according to the transmittance.

Further, in the present invention, the output of the timer 245 is input to the blast control section 243 so that the electromagnetic valve 54 can be opened and closed at predetermined time intervals. Although the control by the timer 245 may be used alone, it is preferable to use it together with the control based on the previous transmittance as described later.

FIG. 4 shows the state of the above control. FIG. 4(a) shows the laser beam transmittance when the solenoid valve 54 of the blaster unit is opened every 60 minutes using the timer 245 as shown in FIG. 4(b). In blasting every 60 minutes, soot and the like are deposited in the optical path, resulting in portions with considerably low transmittance. Continuing the measurement of the gas concentration in this state will cause a decrease in the S/N ratio, and there is a risk that measurement results will appear in which extremely high or low concentrations are presented as noise.

Taking into consideration the intervals at which the transmittance drops rapidly in FIG. 4(a), blasting at equal time intervals with a timer as described above would take about 10 minutes, for example, as shown in FIG. 4(c). However, this would waste too much blast gas.

FIG. 4(d) shows that the electromagnetic valve 54 is opened once every 60 minutes, and in addition, the electromagnetic valve 54 is opened when the transmittance obtained by the calculation unit 241 is less than 10%. It shows the case where

As a result, efficient removal of deposits can be expected.

As described above, it is possible to efficiently blow away the adhering dust and endure long-term use.

30 Flue 40 Installation table 41a Mounting flange 41b Fixed flange 42 Rising pipe 50 Optical path pipe 51a, 51b Flange 52 Blast pipe 54 Solenoid valve 55 Connection port 60 Compression tank 100 Light emission part 110 Light emission window 131 Connection port 141 Light emission control part 142 Light emission Module 200 Light receiving section 210 Light receiving window 300 Blaster unit 241 Calculation section 242 Light receiving module 243 Blast control section 245 Timer

Claims (1)

A laser type gas analyzer comprising a light emitting unit that emits a laser that irradiates a space to be measured through a light emitting window, and a light receiving unit that receives the laser that has passed through the space to be measured through a light receiving window,
a high-pressure tank filled with blast gas;
an optical path tube inserted between the light-emitting window or the light-receiving window and the space to be measured;
a blast tube having a front end communicating with the measurement target space side of the optical path tube and a rear end provided with a connection port to which the high-pressure tank can be attached and detached;
a solenoid valve provided between the blast pipe and the connection port;
An opening/closing control unit that controls opening/closing of the solenoid valve,
The opening/closing control unit
a computing unit that computes the transmittance of the laser from the light-emitting unit to the light-receiving unit;
a control unit that opens the electromagnetic valve for a predetermined time when the calculation unit indicates a transmittance equal to or lower than a predetermined threshold;
a timer that opens the solenoid valve for a predetermined period of time at predetermined intervals;
A laser type gas analyzer, comprising:

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