JP2017116380A - Detector for infrared gas analyzer and infrared gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detector for an infrared gas analyzer that can precisely detect an absorption amount of infrared radiation by a measuring object gas, which is a corrosive gas, by additionally including a simple and low-cost configuration, and an infrared gas analyzer having the detector and conducting a precise gas analysis.SOLUTION: A detector 100 for an infrared gas analyzer includes: a first gas chamber 42; a second gas chamber 43; infrared radiation transmitting windows 44, 45, 46; a first passage 47; a second passage 48; a sensor part storing space 49; ad a DLC protective film 60, coating a surface of the components which is in contact with the same type of a storage gas as the corrosive gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an infrared gas analyzer detector that detects the amount of infrared (IR) absorption by a gas to be measured, and an infrared gas analyzer equipped with the infrared gas analyzer detector.

  When infrared rays pass through a gas, infrared rays having a specific wavelength specific to the gas are absorbed by the gas. An infrared gas analyzer performs an analysis using this phenomenon. The infrared gas is transmitted through the sample gas, the measurement target gas contained in the sample gas absorbs the light, and the infrared light after the absorption is used. The concentration of the measurement target gas contained in the sample gas is measured. As a prior art example of such an infrared gas analyzer, a single beam infrared gas analyzer is known.

  The single beam infrared gas analyzer will be described. As shown in FIG. 3, the infrared gas analyzer 1 includes a light source unit 10, an optical chopper 20, a sample cell 30, and an infrared gas analyzer detector 40.

  The light source unit 10 further includes a light source chamber 11, an infrared light source 12, and an infrared transmission window 13. The light source chamber 11 houses the infrared light source 12. The infrared light source 12 in the light source chamber 11 is connected to a power source and a drive circuit (not shown), generates heat when a drive voltage is applied, and emits infrared rays according to the heat generation temperature. The infrared transmission window 13 transmits this infrared ray. Such a light source unit 10 is disposed on one end side of the sample cell 30 and irradiates infrared rays toward the inside of the sample cell 30. This infrared light passes through the light chopper 20.

  The optical chopper 20 includes a rotating disk 21 and a motor 22. The rotating disk 21 is located between the light source unit 10 and the sample cell 30. The rotating disk 21 is formed with an opening or a notch through which infrared rays pass. When the motor 22 rotationally drives the rotating disk 21, the infrared light emitted from the light source unit 10 is turned on / off at a predetermined period and incident on the sample cell 30 as intermittent infrared light.

  The sample cell 30 includes a cell body 31, sample gas inlets 32 and 33, and infrared transmission windows 34 and 35. The cell body 31 is made of a metal material having corrosion resistance such as stainless steel and has a cylindrical shape, and infrared transmission windows 34 and 35 formed of an infrared transmission material are fixed to both ends thereof. The sample gas is introduced from one of the sample gas inlets 32 and 33, flows through the cell body 31, and then is led out from the other of the sample gas inlets 32 and 33.

  As shown in FIGS. 3 and 4, the infrared gas analyzer detector 40 includes a main body block 41, a first gas chamber 42, a second gas chamber 43, and an infrared transmission unit, which are a combination of divided blocks 41 a and 41 b that are aluminum blocks. Windows 44, 45, 46, a first passage 47 and a second passage 48 are provided. In detail, as shown in FIG. 4, a sensor housing space 49, a sensor 50, a hermetic terminal 51, and a connection terminal (lead pin) 52 are further provided. The infrared gas analyzer detector 40 is disposed on the other end side of the sample cell 30 (opposite side of the light source unit 10).

  3 and 4, the first gas chamber 42 and the second gas chamber 43 of the detector 40 for an infrared gas analyzer are arranged side by side from the sample cell 30 side along the infrared optical path. Yes. In addition, infrared transmissive windows 44, 45, and 46 made of an infrared transmissive material are provided. The first gas chamber 42 and the second gas chamber 43 are partitioned by an infrared transmission window 45. An infrared transmission window 44 is provided on the front side (light source unit side) of the first gas chamber 42, and an infrared transmission window 46 is provided on the rear side of the second gas chamber 43. Such first gas chamber 42 and second gas chamber 43 form a single space. In each of the first gas chamber 42 and the second gas chamber 43, an accommodation gas having the same absorption characteristics as the measurement target gas is sealed.

  Since the contained gas is sealed in the first gas chamber 42 and the second gas chamber 43, it is necessary to keep the airtight stably for a long period of time, and the sensor unit using an adhesive having excellent airtightness such as an epoxy-based adhesive 50 is fixed with no gap.

The first passage 47 is a passage formed in the main body block 41 such that one end communicates with the first gas chamber 42 and the other end communicates with the sensor unit accommodation space 49.
The second passage 48 is a passage formed in the main body block 41 such that one end communicates with the second gas chamber 43 and the other end communicates with the sensor unit accommodation space 49.

A sensor unit 50 is disposed in the sensor unit accommodating space 49.
The sensor unit 50 has a sensor unit passage (broken line portion in FIG. 4) 50a formed therein. One end of the sensor part internal passage 50 a communicates with the first passage 47 and the other end communicates with the sensor part accommodation space 49.

  The hermetic terminal 51 includes a connection terminal (lead pin) 52. The connection terminal (lead pin) 52 formed of a conductive material protrudes in a state where the end is sealed with the hermetic terminal 51. The connection terminal (lead pin) 52 is provided for taking out a detection signal output from the sensor unit 50 to the outside.

  As shown in FIG. 4, the first gas chamber 42 and the second gas are connected to each other by the gas passage including the first passage 47, the sensor portion inner passage 50 a of the sensor portion 50, the sensor portion accommodation space 49, and the second passage 48. The chamber 43 communicates. The mass flow sensor included in the sensor unit 50 detects the flow rate of the stored gas flowing from the first gas chamber 42 to the second gas chamber 43.

  Next, gas analysis by the infrared gas analyzer 1 of the prior art example will be described. For example, when measuring the concentration of CO gas as the measurement target gas, a relatively high concentration of CO gas is enclosed as the contained gas in the first gas chamber 42 and the second gas chamber 43 of the detector 40 for infrared gas analyzer. . As shown in FIG. 3, in the sample cell 30, the sample gas is introduced from one of the sample gas inlets 32 and 33 and is circulated in the sample cell 30.

  The infrared rays emitted from the infrared light source 12 are turned on and off at a predetermined cycle by a rotating disk 21 that is driven to rotate by a motor 22 to become an infrared ray of intermittent light. The infrared light enters the sample cell 30 whose both ends are sealed by the infrared transmission windows 34 and 35, and passes through the sample gas containing the CO gas as the measurement target gas. This infrared ray is repeatedly reflected in the sample cell 30. At this time, infrared rays are absorbed with an absorption amount corresponding to the concentration of CO gas contained in the sample gas.

  The infrared light after the absorption is performed in this way passes through the infrared transmission window 35 and enters the detector 40 for the infrared gas analyzer. In this infrared gas analyzer detector 40, infrared light that has passed through the sample cell 30 in the preceding stage is incident on the first gas chamber 42 and the second gas chamber 43.

  The first gas chamber 42 and the second gas chamber 43 are filled with a containing gas (CO gas) having the same absorption characteristics as the measurement target gas. Infrared light emitted from the light source is first partially absorbed by the gas contained in the first gas chamber 42 (CO gas), and then the remainder is absorbed by the gas contained in the second gas chamber 43 (CO gas). Is done. This infrared ray is a heat source, and the volume of each contained gas (CO gas) in the first gas chamber 42 and the second gas chamber 43 expands in proportion to the amount of infrared absorption, and the first gas chamber 42 and the second gas. A pressure increase occurs in the chamber 43.

  Therefore, due to the pressure difference based on the difference in the amount of infrared absorption of the stored gas in the first gas chamber 42 and the second gas chamber 43, the direction of the arrow G from the first gas chamber 42 to the second gas chamber 43 (see FIG. 4). A minute gas flow occurs. The flow from the first passage 47 provided in the main body block 41 to the second passage 48 provided in the main body block 41 through the sensor portion inner passage 50a and the sensor portion accommodation space 49 of the sensor portion 50.

  A minute gas flow flowing between the first gas chamber 42 and the second gas chamber 43 so as to be proportional to such a concentration is detected by the sensor unit 50 as a resistance change corresponding to a change in pressure or flow rate. A detection signal V is output. The detection signal V is configured to be converted into an electrical signal (gas concentration signal) by an arithmetic processing circuit (not shown) and output to the outside. Then, for example, the gas concentration of the measurement object gas (CO gas) can be obtained by the “Lambert-Beer equation”.

  In addition, the prior art of the detector for infrared gas analyzers which has the same structure is disclosed by patent document 1, patent document 2, etc., for example.

JP 2013-185867 A (FIGS. 1 and 4) Japanese Patent Laid-Open No. 2000-97855 (FIG. 2)

  The gas contained in the detector 40 for the infrared gas analyzer is composed of materials constituting the detector, such as an adhesive, a sensor element material, a constituent material for the main body block, a wiring material, and an infrared transmission window material. From the standpoint of stability, the reactivity is low and the gas composition does not change over a long period of time. The accommodation gas of the prior art described above is a CO gas with relatively low reactivity and is stable.

However, when it is desired to measure the concentration of SO ₂ gas as the measurement target gas, it is necessary to enclose the high concentration SO ₂ gas in the detector 40 for the infrared gas analyzer. The SO ₂ gas is corrosive, and the gas composition of the stored gas may change due to problems such as reaction with the adhesive and corrosion of the sensor material. When the gas composition change of the contained gas occurs, a drift phenomenon and sensor element deterioration occur, and the detector life is significantly shortened. It has been found that a detector for an infrared gas analyzer and an infrared gas analyzer may be difficult to detect a corrosive gas.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to detect infrared rays absorbed by a measurement target gas that is corrosive gas with high accuracy by adding a simple and inexpensive configuration. An object of the present invention is to provide a gas analyzer detector and an infrared gas analyzer equipped with the infrared gas analyzer detector for performing highly accurate gas analysis.

Therefore, in the invention according to claim 1 of the present invention,
A sensor unit;
First and second gas chambers in which the contained gas is sealed, a sensor portion accommodating space for accommodating the sensor portion, a first passage having one end communicating with the first gas chamber and the other end communicating with the sensor portion accommodating space. A body block having one end communicating with the second gas chamber and the other end communicating with the sensor unit accommodating space, respectively.
Infrared gas comprising: a DLC protective thin film coated on at least a surface of the first gas chamber, the second gas chamber, the sensor housing space, the first passage, and the second passage that contacts the containing gas. It was set as the detector for analyzers.

In the invention according to claim 2 of the present invention,
In the main body block, the first and second gas chambers are defined by two metal divided blocks and three infrared transmitting windows that transmit infrared light.
Of the three infrared transmitting windows, the DLC protective thin film is coated on the front and back surfaces of one infrared transmitting window that partitions the first and second gas chambers, and the remaining two infrared transmitting windows are indoors. One surface of the DLC protective film is coated with the DLC protective thin film.

In the invention according to claim 3 of the present invention,
A light source unit that emits infrared rays, a sample cell that circulates a sample gas containing a measurement target gas and absorbs infrared rays from the light source unit by the measurement target gas, and infrared rays by the measurement target gas based on infrared rays that have passed through the sample cell An infrared gas analyzer comprising the detector for infrared gas analyzers according to claim 1 or 2 that outputs a detection signal proportional to the amount of absorption.

  According to the present invention, by adding a simple and inexpensive configuration, a detector for an infrared gas analyzer that detects the amount of infrared rays absorbed by a measurement target gas that is a corrosive gas with high accuracy, and the infrared gas analyzer. It is possible to provide an infrared gas analyzer equipped with a detector and performing highly accurate gas analysis.

It is a block diagram of the detector for infrared gas analyzers of the form for implementing this invention. It is a wavelength-transmittance characteristic figure for demonstrating the transmittance | permeability of the infrared transmission window which changes with the presence or absence of a DLC protective thin film. It is a block diagram of an infrared gas analyzer. It is a block diagram of the detector for infrared gas analyzers.

  Then, the detector for infrared gas analyzers and the infrared gas analyzer of the form for implementing this invention are demonstrated. In the present invention, the structure of the infrared gas analyzer detector 100 (see FIG. 1) is novel.

  Hereinafter, the infrared gas analyzer of the present invention is replaced with the infrared gas analyzer detector 100 (FIG. 1) of the present invention instead of the infrared gas analyzer detector 40 (see FIG. 4) of the infrared gas analyzer 1 of FIG. The light source unit 10, the optical chopper 20, and the sample cell 30 other than the above are assumed to have the same configuration, and redundant description is omitted.

  The infrared gas analyzer detector 100 also has a main body block 41, a first gas chamber 42, a second gas chamber 43, infrared transmission windows 44, 45, 46, a first passage, except that a DLC protective thin film is added. 47, the second passage 48, the sensor portion accommodating space 49, the sensor portion 50, the hermetic terminal 51, and the connection terminal (lead pin) 52 have the same configuration and function, and thus redundant description is omitted. Hereinafter, the DLC protective thin film will be described mainly.

  As shown in FIG. 1, the infrared gas analyzer detector 100 includes a first gas chamber 42, a second gas chamber 43, infrared transmission windows 44, 45, 46, a first passage 47, a second passage 48, and a sensor. A DLC protective thin film 60 made of DLC (diamond-like carbon) is coated on at least a surface of the partial housing space 49 that is in contact with the containing gas.

  The DLC protective thin film 60 can be coated by a method such as CVD, EV vapor deposition, or sputtering, and can be formed with an optimum film thickness even in a complicated shape. The film to be coated can be made from several microns to several thousand microns thick. As in the present invention, the first gas chamber 42, the second gas chamber 43, the infrared transmission windows 44, 45, 46, the first passage 47, the second passage 48, and the sensor portion accommodation space 49 can be formed. .

  For example, DLC (diamond-like carbon) is formed on the entire surface of each part by a method such as CVD, EV vapor deposition, or sputtering with respect to the divided blocks 41a and 41b and the infrared transmitting windows 44, 45, and 46 in the parts state before assembly. The first gas chamber 42, the second gas chamber 43, the infrared transmitting windows 44, 45, 46, the first passage 47, the second passage 48, and the sensor unit accommodating space 49 are assembled on the surface of the DLC. A protective thin film 60 may be formed.

Next, the reason why this DLC (diamond-like carbon) is employed will be described. DLC (diamond-like carbon) is generally used as a corrosion-resistant coating film with little reactivity with corrosive components (for example, SO ₂ gas and NO gas).

  Another property of DLC (diamond-like carbon) is that it has good infrared transmission characteristics in a wide infrared wavelength range and can be applied as a coating film for optical elements using infrared rays.

Consider infrared transmission windows. FIG. 2 shows infrared transmission characteristics when a DLC (diamond-like carbon) thin film is coated on an infrared transmission window made of calcium fluoride (CaF ₂ ). The transmittance is secured about 90% or more in the range of 2 to 6 microns, which is the wavelength of infrared rays, and it can be seen that a large sensitivity loss does not occur.

  In the present invention, as shown in FIG. 1, DLC (diamond-like carbon) thin films are formed on one side of the infrared transmission windows 44 and 46 and on both sides of the infrared transmission window 45. This minimizes sensitivity loss.

  However, although not shown, a DLC (diamond-like carbon) thin film may be formed on both the front and back surfaces of all of the infrared transmission windows 44, 45, and 46. In this case, it is not necessary to make a separate infrared transmission window, and the manufacturing process can be simplified.

Although not shown, the DLC protective thin film 60 may be formed by coating DLC (diamond-like carbon) on the sensor passage 50a or the surface of the sensor portion 50.
Although not shown, in addition to the detector 100 for the infrared gas analyzer, on the inner surfaces of the cell body 31 and the infrared transmitting windows 34 and 35 that form an internal space through which the sample gas passes among the sample cells 30. Alternatively, the DLC protective thin film 60 may be formed by coating DLC (diamond-like carbon).

As described above, the first gas chamber 42, the second gas chamber 43, the infrared transmission windows 44, 45, 46, the first passage 47, the second passage 48, and the surface of the sensor housing space 49 of the detector 100 for an infrared gas analyzer. By forming the DLC protective thin film 60, there is an effect of greatly improving the stability of the contained gas while maintaining the infrared detection characteristics. For example, even when a corrosive gas such as SO ₂ is encapsulated in the infrared gas analyzer detector 100 as a containing gas, the DLC protective thin film 60 suppresses the occurrence of corrosion and reduces the change in gas composition, so that the composition is stable over a long period of time. Can be maintained.

The infrared gas analyzer detector 100 of the present invention described above has the following advantages.
(1) Corrosion resistance was improved while maintaining detection performance.
Compared to conventional devices, the detector for infrared gas analyzers only adds a DLC protective thin film, which improves the corrosion resistance without changing the design of the detector in particular, and in the same detection conditions and gas filling conditions. There is an advantage that the detection performance can be maintained without causing a large sensitivity loss.

(2) Realize stable gas analysis over a long period of time.
According to the present invention, the surface in contact with the corrosive measurement target gas or the contained gas is coated with the DLC protective thin film. This prevents, for example, adhesives, sensor element materials, body block components, wiring materials, infrared transmission window materials, etc. from reacting with corrosive measuring gas or containing gas, that is, reducing the measuring gas or containing gas. It is possible to prevent a situation in which the gas composition is changed by preventing the gas composition and to stably measure the gas concentration over a long period of time.

(3) It is easy to form the DLC protective thin film of the present invention.
The DLC protective thin film 60 can be coated by a method such as CVD, EV vapor deposition, or sputtering. When the main body block 41 is viewed, not only the first gas chamber 42 and the second gas chamber 43, A protective layer can be formed with an optimum film thickness on the surfaces of the first passage 47, the second passage 48, and the sensor portion accommodation space 49 in the recessed portion. In addition, since the coating film can be manufactured in a wide range from several microns to several thousand microns, it is possible to coat a complex part such as a sensor or a channel with an optimum film thickness.

  The present invention as described above can be used for an infrared gas analyzer that measures the concentration of a measurement target gas contained in a sample gas by using the infrared absorption effect inherent to gas molecules. Used for process monitoring related to gas concentration, combustion gas analysis in boilers and furnaces, air pollution monitoring, measurement of automobile exhaust gas, etc.

1: Infrared gas analyzer 10: Light source unit 11: Light source chamber 12: Infrared light source 13: Infrared light transmission window 20: Optical chopper 21: Rotating disk 22: Motor 30: Sample cell 31: Cell body 32, 33: Sample gas inlet / outlet 34, 35: Infrared transmission window 100: Detector for infrared gas analyzer 41: Main body block 42: First gas chamber 43: Second gas chamber 44, 45, 46: Infrared transmission window 47: First passage 48: Second Passage 49: Sensor unit accommodation space 50: Sensor unit 51: Hermetic terminal 52: Connection terminal (lead pin)
60: DLC protective thin film

Claims (3)

A sensor unit;
First and second gas chambers in which the contained gas is sealed, a sensor portion accommodating space for accommodating the sensor portion, a first passage having one end communicating with the first gas chamber and the other end communicating with the sensor portion accommodating space. A body block having one end communicating with the second gas chamber and the other end communicating with the sensor unit accommodating space, respectively.
Infrared gas comprising: a DLC protective thin film coated on at least a surface of the first gas chamber, the second gas chamber, the sensor housing space, the first passage, and the second passage that contacts the containing gas. Detector for analyzer. In the main body block, the first and second gas chambers are defined by two metal divided blocks and three infrared transmitting windows that transmit infrared light.
Of the three infrared transmitting windows, the DLC protective thin film is coated on the front and back surfaces of one infrared transmitting window that partitions the first and second gas chambers, and the remaining two infrared transmitting windows are indoors. An infrared gas analyzer detector, wherein the DLC protective thin film is coated on one surface.   A light source unit that emits infrared rays, a sample cell that circulates a sample gas containing a measurement target gas and absorbs infrared rays from the light source unit by the measurement target gas, and infrared rays by the measurement target gas based on infrared rays that have passed through the sample cell An infrared gas analyzer comprising: the detector for an infrared gas analyzer according to claim 1 or 2 that outputs a detection signal proportional to the amount of absorption of the infrared gas analyzer.

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