JPH09178655A - Infrared gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared gas analyzer which measures multiple gas component with high precision without being accompanied by a complex work, with simple constitution. SOLUTION: A measurement cell 4 in which sample gas flows continuously is irradiated with the infrared ray from a light source 1 through an optical filter 3 and a correlation filter 2, and the infrared ray passing through the measurement 4 is detected by a detector 5, and concentration of to-be-measured gas is calculated with a data process part 6. At this time, only by exchanging the correlation filter 2, measurement of concentration of different gas is enabled, so that no conventional troublesome work that the optical filter is detached from the measurement cell is required, so that, handling of the device is simplified and the entire measurement time is shortened by the saved time.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is used for process control relating to gas concentration in chemical plants and steel mills, flue gas analysis of boilers and combustion furnaces, air pollution monitoring, automobile exhaust gas measurement, etc. The present invention relates to an infrared gas analyzer for continuously measuring the concentration of a specific component in gas and vapor by utilizing the infrared absorption effect of the above, and particularly to an infrared gas analyzer equipped with a correlation filter.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional infrared gas analyzer equipped with a correlation filter. As shown in FIG. 3a, infrared light from a light source 11 passes through a correlation filter 12 and an inlet 14a. The sample gas is further introduced and discharged from the discharge port 14b, so that the measurement cell 14 in which the sample gas is continuously flowed is irradiated.

As shown in FIG. 3b, the correlation filter 12 has two CO cells 12a and N each containing a gas (CO) to be measured and a so-called zero gas (N ₂ ) that does not absorb infrared light. _{With two} cells 12b, FIG. 3a
Is appropriately rotated by a motor 12z.

The detector 15 alternately detects infrared light obtained through the CO cell 12a of the correlation filter 12 and infrared light obtained through the N2 cell 12b.
6 calculates the CO concentration in the sample gas from the data detected alternately.

That is, since the infrared light transmitted through the CO cell 12a completely absorbs the infrared light in the absorption wavelength band of CO, the data detected by the detector 15 is
Regardless of the CO concentration in 4, the CO absorption wavelength band component of the infrared light becomes zero, while the infrared light transmitted through the N2 cell 12a remains the CO absorption wavelength band infrared light.
The data detected by the detector 15 is C in the measuring cell 14.
The value corresponds to the O concentration. For this reason, the data processing unit 16
By calculating the ratio between the two, the CO concentration in the sample gas is calculated.

Here, the optical filter 13 provided in the measuring cell 14 has a function of transmitting only infrared light in the absorption wavelength band of CO, whereby the absorption wavelength band is close to CO such as CO _{2 and the} like. It is possible to eliminate the interference error due to the gas component.

[0007]

However, in such an infrared gas analyzer, for example, when it is desired to measure a gas component concentration different from CO, the optical filter 13 as well as the correlation filter 12 needs to be replaced with one corresponding to the gas component. Therefore, the removal work from the measurement cell 14 was very troublesome.

On the other hand, as shown in FIG. 4, CO cells 2a 'and C filled with CO gas and CO ₂ gas, respectively.
O ₂ cell 2b 'and N ₂ cell 2 filled with zero gas
When the correlation filter 2 ′ having c ′ is used, it is possible to analyze a plurality of gas components without replacing the correlation filter 2 ′. In such a case, the optical filter absorbs all the gas components to be measured. It is necessary to use one that passes the wavelength band, which complicates the configuration. In addition, CO gas and CO
_{In the} case of simultaneous measurement of gases such as _two gases whose absorption wavelength bands are close to each other, the measurement error caused by each interference cannot be avoided.

Therefore, an object of the present invention is to provide an infrared gas analyzer having a simple structure and capable of measuring a plurality of gas components with high accuracy without complicated work.

[0010]

The present invention has a measuring cell in which a sample gas continuously flows, and detects infrared light transmitted through the measuring cell obtained through a correlation filter to detect a specific gas. An infrared gas analyzer for analyzing components, wherein the correlation filter is provided with an optical filter that allows only infrared light in the absorption wavelength band of the measurement target gas to pass therethrough.

Such a correlation filter has a gas cell in which a plurality of gases to be measured are individually enclosed, and an optical filter which passes only infrared light in the absorption wavelength band of the gas enclosed in each gas cell is individually provided. It is characterized in that it is provided.

Further, in the above-mentioned correlation filter, zero gas cells filled with zero gas are arranged adjacent to the respective gas cells, and only the infrared light in the absorption wavelength band of the corresponding gas is arranged on the respective gas cells and the adjacent zero gas cells. It is characterized in that an optical filter for passing the light is provided.

In the above correlation filter, when detecting two-component gas, a first gas cell filled with a first gas and a second gas cell filled with a second gas are provided, and a first gas cell is filled with zero gas. A first zero gas cell used for gas detection and a second zero gas cell used for second gas detection are arranged adjacent to each other, and infrared light in the absorption wavelength band of the first gas is provided on the first gas cell and the first zero gas cell. A first optical filter that passes only the second optical filter, and a second optical filter that passes only infrared light in the absorption wavelength band of the second gas on the second gas cell and the second zero gas cell. It is characterized in that a communication hole for communicating the zero gas cell and the second zero gas cell is formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an overall schematic view of an infrared gas analyzer according to the present invention. Infrared light emitted from a light source 1 passes through a correlation filter 2 which is rotationally driven by a motor 2z,
The measurement cell 4 is irradiated.

The correlation filter 2 is provided with an optical filter 3 which allows only infrared light in the absorption wavelength band of the specific gas to pass therethrough, so that the interference of other gas components whose absorption wavelength band is close to the specific gas. The error can be eliminated.

FIG. 2 shows a correlation filter 2 and an optical filter 3.
FIG. 2a shows a top view thereof, and FIG. 2b shows a side view thereof. In the figure, the correlation filter 2 is a CO gas filled with CO.
Cell 2a, O filled with CO ₂ gas and filled with CO ₂ cell 2b, so-called zero gas (N ₂ ) that does not absorb infrared light
The N ₂ cell 2c for CO ₂ and the N ₂ cell 2d for CO ₂ are formed in the same shape at substantially equal intervals.

And, which is one side of the correlation filter 2,
On the CO cell 2a and the CO N ₂ cell 2c, a CO optical filter 3a for transmitting only infrared light in the CO absorption wavelength band.
But also, on the CO ₂ cell 2b and CO ₂ for N ₂ cell 2d, and transmits infrared light absorption wavelength band of CO ₂ CO ₂ alone
Optical filters 3b for use are respectively provided. The N ₂ cell 2c for CO and the N ₂ cell 2d for CO ₂ are internally connected via the communication hole 2e. This allows
Since the zero gas need only be filled once, the gas filling work is simplified.

The CO optical filter 3a and the CO ₂ optical filter 3b function as a conventional window material, that is, C.
It also has a function of sealing the gas in the O cell 2a and the N ₂ cell for CO 2c, and is disposed on the correlation filter 2 by an adhesive agent or a screw. On the other surface of the correlation filter 2, a conventional window member 2f that transmits infrared light and seals gas in the cell is provided.

In FIG. 1, the sample gas is introduced into the measuring cell 4 through the inlet 4a and discharged through the outlet 4b, so that the sample gas is continuously flowed, and the optical filter is used. The infrared light that has passed through 3 and the correlation filter 2 is
It passes through the sample gas in the measurement cell 4 through the window 4d and reaches the detector 5 through the window 4c.

The detector 5 individually detects the infrared intensity in the absorption wavelength band of the specific gas component, in this embodiment, the infrared intensity in the absorption wavelength band of CO and CO ₂ and outputs it to the data processing unit 6. The detector used here is an infrared sensor such as a PbSe sensor or a pyroelectric sensor. The data processing unit 6 calculates the concentration of the measurement target gas from the detection data of infrared light that has passed through the cell in which the measurement target gas of the correlation filter 2 is filled and the cell in which the zero gas is filled.

Next, the operation of the present invention will be described.
By driving the motor 2z, the CO cell 2a, the CO N ₂ cell 2c, and the CO ₂ N ₂ arranged in the correlation filter 2 are driven.
The cell 2d and the CO ₂ cell 2b are sequentially measured and the window 4 of the cell 4 is measured.
The infrared light transmitted through the respective cells and the measuring cell 4 is positioned on d and detected sequentially by the detector 5.

Here, the infrared light transmitted through the CO cell 2a is the infrared light in the absorption wavelength band of CO, and the CO ₂ cell 2
Since the infrared light transmitted through b is completely absorbed in the CO ₂ absorption wavelength band, the data detected by the detector 5 is the CO and CO ₂ concentrations in the measurement cell 4. Irrespective of the CO absorption wavelength band of infrared light and CO ₂
The absorption wavelength band component of becomes a value of zero.

On the other hand, the infrared light transmitted through the CO N ₂ cell 2c remains as it is in the absorption wavelength band of CO.
The data detected by the detector 5 has a value corresponding to the CO concentration in the measurement cell 4, and the infrared light transmitted through the CO ₂ N ₂ cell 2d is the infrared light in the CO ₂ absorption wavelength band as it is. Since it remains, the data detected by the detector 5 has a value corresponding to the CO ₂ concentration in the measuring cell 4.

Therefore, in the data processing unit 6, the CO cell 2
from the ratio of the detection value of the infrared light absorption wavelength band of CO passing through the N ₂ cell 2c for a and CO, CO concentration in the sample gas is calculated, the CO ₂ cell 2b and CO ₂ for N ₂ cell 2d From the ratio of the infrared light detection values in the absorption wavelength band of the transmitted CO ₂ ,
The CO ₂ concentration in the sample gas is calculated.

Here, the CO cell 2a and the CO N ₂ cell 2
Since the optical filter 3a for CO and the optical filter 3b for CO ₂ are provided on the CO, the CO ₂ cell 2b, and the CO ₂ N ₂ cell 2d, respectively, the light passing through each cell is Infrared light and C having only absorption wavelength band of
The infrared light has only the absorption wavelength band of O ₂ , and even when detecting CO and CO ₂ which have absorption wavelength bands close to each other,
The measured CO and CO ₂ concentrations are highly accurate because they do not interfere with each other.

Further, since the optical filter 3 is provided in the correlation filter 2, when the concentration measurement of different gases is performed, the complicated operation of removing the optical filter from the measuring cell as in the prior art is required only by exchanging the correlation filter. Since it is not necessary at all, the handling of the device is simplified and the entire measurement time is shortened accordingly.

In the above-mentioned embodiment, an example of measuring the gas concentrations of two components has been shown, but it is also possible to detect the gas concentrations of two or more kinds in the same manner, and to measure the gas concentration of one component. It is also applicable in some cases.

Further, although the correlation filter 2 is arranged between the light source 1 and the measuring cell 4, it may be arranged between the measuring cell 4 and the detector 5.

[0030]

According to the present invention, when measuring the concentrations of different gases, the troublesome work of removing the optical filter from the measuring cell as in the conventional case is not necessary at all by simply replacing the correlation filter. The handling of the device is simplified and the total measurement time is shortened accordingly.

Further, when measuring two or more kinds of gases with one correlation filter, even if the gases having the absorption wavelength bands of infrared light are close to each other, there is no interference with other gases, so that it is extremely effective. It is possible to measure the gas concentration with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an infrared gas analyzer according to the present invention.

FIG. 2 is a diagram showing an embodiment of a correlation filter and an optical filter according to the present invention.

FIG. 3 is a diagram showing a conventional infrared gas analyzer and a correlation filter.

FIG. 4 is a diagram showing a correlation filter for measuring a conventional multi-component gas.

[Explanation of symbols]

 1 ... Light source 2 ... Correlation filter 3 ... Optical filter 4 ... Measurement cell 4a ... Inlet port 4b ... Outlet port 5 ... Detector 6 ...・ Data processing unit

Claims (2)

[Claims] 1. An infrared gas analyzer for analyzing a specific gas component by having a measuring cell in which a sample gas continuously flows, and detecting infrared light transmitted through the measuring cell obtained through a correlation filter. An infrared gas analyzer, wherein the correlation filter is provided with an optical filter that allows only infrared light in the absorption wavelength band of the measurement target gas to pass therethrough. 2. The optical filter, wherein the correlation filter has a gas cell in which a plurality of gases to be measured are individually enclosed, and which passes only infrared light in the absorption wavelength band of the gas enclosed in each gas cell. The infrared gas analyzer according to claim 1, wherein the infrared gas analyzer is provided separately.