JP2020169910A - Laser type gas analyzer - Google Patents

Abstract

To provide a laser type gas analyzer with which the permeability of an optical path is not degraded by soot, etc., even when used for long hours.SOLUTION: The present invention pertains to a laser type gas analyzer. A high-pressure tank is filled with blast gas, and an optical path tube is inserted between a light-emission window or a light-receiving window and a measurement object space. Furthermore, the tip of a blast tube (on measurement object space side) communicates with the optical path tube, and a connecting port to which the high-pressure tank is attachable/removal is provided at the rear end of the blast tube. An electromagnetic valve is provided between the connecting port and the blast tube, and an opening/closing control unit for controlling the opening/closing of the electromagnetic valve is further provided. The opening/closing control unit concurrently uses the permeability of laser from the light-emitting part to the light-receiving part and control by a timer.SELECTED DRAWING: Figure 2

Description

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

FIG. 5 shows an example in which a laser gas analyzer is applied to a flue (measurement target space), and FIG. 6 shows a three-dimensional view of the light emitting side thereof. For example, the contents of US Pat. No. 9,294,003 Is a more schematic representation of.

The laser light emitted from the light emitting unit 100 is emitted to the flue 30 which is the measurement target space through the light emitting window 110, and the laser light passing through the flue 30 is received by the light receiving unit 200 through the light receiving window 210. To. Here, the light emitting unit 100, the light receiving unit 200, and the flue 30, which is the measurement target space, are partitioned by the light emitting window 110 and the light receiving window 210.

A mounting flange 41a is provided on the flue 30 side of the light emitting window 110 of the light emitting unit 100, and a purge gas connection port 131 described later is provided between the mounting flange 41a 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 form an installation base 40. ing. The mounting flange 41a is fixed to the fixed flange 41b, whereby the light emitting portion 100 is fixed to the installation base 40 of the flue 30.

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 purge gas of about 50 to 100 L / min is always connected to the riser pipe 42. To keep the window 110 of the light emitting unit 100 clean. This configuration 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 on the measurement target space side of the light emitting window 110 and the measurement target space side of the light receiving window 210, dust adheres to the light emitting window 110 and the light receiving window 210. It is reduced and the decrease in light receiving intensity is suppressed.

However, when there are various types of incinerated materials such as urban waste incineration facilities, the flue contains coexisting gas with high adsorptivity, moisture, dust, etc. in addition to the gas to be measured. Therefore, depending on the flow velocity in the flue, dust is accumulated inside the riser tube 42 of the installation table 40 which is an optical path, and the optical path tube is blocked, so that the laser light received by the light receiving unit 200 is received. The intensity will decrease, causing a decrease in the S / N ratio in the measured value.

The method of flowing the purge gas is effective for the operation of the process for a short time, but it cannot be said that it is sufficient because the phenomenon of dust accumulating and blocking the inside of the vicinity of the riser pipe 42 is observed in the operation for a long time. is the current situation.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and provides a laser gas analyzer capable of securing an optical path even in long-term operation.

The present invention relates to a laser gas analyzer including a light emitting unit that emits a laser that irradiates a measurement space through a light emitting window and a light receiving unit that receives a 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 measurement target space. Further, the tip of the blast tube (on the measurement target space side) communicates with the optical path tube, and a connection port to which the high pressure tank can be attached and detached is provided at the rear end of the blast tube. A solenoid valve is provided between the connection port and the blast pipe, and an opening / closing control unit for controlling the opening / closing of the solenoid valve is further provided.

As the opening / closing control unit, a timer that opens the solenoid valve at predetermined intervals for a predetermined time can be used. Further, it is also possible to provide a calculation unit for calculating the transmittance of the laser from the light emitting unit to the light receiving unit so that the open / close control unit opens for a predetermined time according to the transmittance. Further, the control by the timer and the control based on the transmittance may be used together.

With the above configuration, the blast gas can be ejected into the start-up pipe of the installation stand as needed, so that the adhering dust can be efficiently blown off, and it can withstand long-term use. In particular, it is effective to use both the solenoid valve control based on the transmittance of the optical path tube and the solenoid valve control based on the timer.

It is a perspective view of the whole invention. It is an exploded perspective view of this invention. It is a block diagram which shows the control unit of this invention. It is a figure explaining the blast control by this invention. It is a conceptual diagram of the conventional laser type gas analyzer. It is a three-dimensional view which shows the light emitting side of FIG.

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 a symmetrical structure, only the structure of the light emitting side is shown in FIGS. 1 and 2.

As described above, the mounting flange 41a is provided on the flue 30 side of the light emitting window 110 of the light emitting unit 100, and the fixed flange 41b corresponding to the mounting flange 41a is provided at the rear end of the rising pipe 42 of the flue 30. Is provided.

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

The rear end (light emitting portion side, light receiving portion side) of the optical path tube 50 having a predetermined length has a flange 51a that matches the mounting flange 41a, and the tip (flue side) has a flange that matches the fixed flange 41b. 51b is provided. The tip of the blast tube 52 communicates with the optical path tube 50 at an acute angle with respect to the axial direction of the optical path tube 50 and communicates with the flange 51b side, and the solenoid valve 54 is attached to the rear end of the blast tube 52. The connection port 55 of the compression tank 60 is provided via the connection port 55.

The blaster unit 300 configured as described above is inserted between the mounting flange 41a and the fixing flange 41b of the installation base 40 to fix the mounting flange 41a and the flange 51a and the fixing flange 41b and the flange 51b. 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, and further, a compression tank for nitrogen gas or instrumentation air is connected to the connection port 55. Connect 60.

With the above configuration, by opening the solenoid valve 54, it is possible to blow off the dust accumulated near the opening of the optical path tube 50 to the flue 30.

FIG. 3 is a block diagram showing a control circuit for controlling the opening and closing of the solenoid valve 54.

A drive current in which a sawtooth wave of about several tens to several hundreds Hz is superimposed on a sawtooth wave of about several tens to several hundreds Hz is applied to the light emitting module 142 from the light emission control unit 141 of the light emitting unit 100, and a tunable laser is emitted from the light emitting window 110. It emits light. After passing through the measurement target space (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 measurement target gas in the measurement target space, but in the present invention, in addition to the calculation of the concentration, the transmittance, that is, the intensity of the light emitted from the light emitting module 142. 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 light receiving intensity to the light emitting intensity thus obtained is input to the blast control unit 243, and when the light receiving intensity / light emitting intensity is equal to or less than a predetermined threshold value (for example, 10%), the blast control is performed. The unit 243 opens the solenoid valves 54 on the light emitting side and the light receiving side for a predetermined time. This makes it possible to control the opening and closing of the solenoid valve 54 according to the transmittance.

Further, in the present invention, the output of the timer 245 can be input to the blast control unit 243 to open and close the solenoid valve 54 at predetermined time intervals. The control by the timer 245 may be used alone, but as will be described later, it is preferable to use it in combination with the control based on the early transmittance.

FIG. 4 shows the state of the above control. FIG. 4A shows the transmittance of laser light when the solenoid valve 54 of the blaster unit is opened every 60 minutes using a timer 245 as shown in FIG. 4B. In the blast every 60 minutes, soot and the like are deposited in the optical path, so that a portion having a considerably low transmittance is generated. If the measurement of the gas concentration is continued in this state, the S / N ratio may be lowered, and a measurement result showing an extremely high or low concentration as noise may appear.

In consideration of the interval at which the transmittance drops sharply in FIG. 4 (a), if the timer tries to blast at equal time intervals as described above, it will be about every 10 minutes, for example, as shown in FIG. 4 (c). However, this wastes too much blast gas.

FIG. 4D shows that the solenoid valve 54 is opened once every 60 minutes, and in addition, the solenoid valve solenoid valve 54 is opened when the transmittance obtained by the calculation unit 241 is less than 10%. It shows the case of.

This can be expected to result in efficient sediment removal.

As described above, the adhering dust can be efficiently blown off, and it can withstand long-term use.

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

Claims (4)

In a laser gas analyzer including a light emitting unit that emits a laser that irradiates a measurement space through a light emitting window and a light receiving unit that receives a laser that has passed through the measurement target space through a light receiving window.
A high-pressure tank filled with blast gas and
An optical path tube inserted between the light emitting window or the light receiving window and the measurement target space,
A blast tube whose tip communicates with the optical path tube and whose rear end is provided with a connection port to which the high-pressure tank can be attached and detached.
A solenoid valve provided between the high-pressure tank and the connection port,
A laser gas analyzer comprising an opening / closing control unit for controlling the opening / closing of the solenoid valve. The laser gas analyzer according to claim 1, wherein the opening / closing control unit includes a timer that opens the solenoid valve at predetermined intervals for a predetermined time. The open / close control unit
An arithmetic unit that calculates the transmittance of the laser from the light emitting unit to the light receiving unit,
The laser gas analyzer according to claim 1, further comprising a control unit that opens the solenoid valve for a predetermined time when the calculation unit exhibits a transmittance below a predetermined threshold value. The open / close control unit
An arithmetic unit that calculates the transmittance of the laser from the light emitting unit to the light receiving unit,
A control unit that opens the solenoid valve for a predetermined time when the calculation unit exhibits a transmittance below a predetermined threshold value.
The laser gas analyzer according to claim 1, further comprising a timer that opens the solenoid valve at predetermined intervals for a predetermined time.

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