JPS6024420B2 - gas analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analyzer in which a light source, a cell, and a detector are arranged in series, and a pressurized gas is introduced into the cell.

FIG. 1 shows an example of a double beam non-dispersive infrared analyzer that is commonly used as this type of analyzer.

This analyzer has two optical paths created by two light sources 11 and 12, with a comparison cell 13 on one side and a sample cell 1 on the other side.
4 is provided, and the light passing through each cell 13, 14 is sent to the chopper 1.
5, the light enters the left and right compartments 16a, 16b of the detector 16 intermittently. Mike. The concentration of the component gas to be measured in the sample cell 14 is measured by detecting it with the phone 17. By the way, in this analyzer, each light source 1
1, 12 and cells 13, 14 a, b, each cell 13,
14 and the detector 16, and if a component gas to be measured or a gas having similar infrared absorption enters into this space, an error will occur in the measurement.

In particular, when measuring low concentration gas using a short cell or when measuring carbon dioxide, etc. contained in large amounts in the atmosphere, this error poses a major hindrance to measurement. This problem is not limited to double-beam analyzers, but also exists in the single-beam analyzer shown in FIG.
The same problem occurs because there is a dead space e between the cell 22 and the detector 23, and a dead space f between the cell 22 and the detector 23.

In other words, regardless of the type or type of analyzer that has a light source, cell, and detector arranged in series, there will always be a dead space between the light source, cell, and detector, so the problem described above is caused by this problem. This is a common problem with analyzers. Conventionally, attempts have been made to solve this problem by sealing the dead space with a ring, or by purging the area around the analyzer with a gas that does not interfere with the component gas being measured, but both methods are expensive. It is expensive, and the latter method requires a large-scale device as a whole, and also requires a separate pump or the like to supply purge gas.

In this respect, the present invention is a novel method that can reliably prevent atmospheric gas from entering the dead space and perform highly accurate measurements without using an O-ring or purging with a gas that does not interfere with the components being measured. Moreover, the present invention aims to provide a useful gas analyzer.

Next, an embodiment of the present invention will be described based on FIGS. 3 to 5.

3 and 4 both show the light sources 31, 41 and the sample cell 3.
2, 42, shows a single beam type infrared gas analyzer in which detectors 33, 43 are arranged in series, and the analyzer shown in FIG. 3 has a chopper 34 between the cell 32 and the detector 33,
On the other hand, the analyzer shown in FIG. 4 has a chopper 4.4 between the light source 41 and the cell 42. In these analyzers, the sample cells 32 and 42 are placed at appropriate positions that do not block the optical path.
For example, gas inlet ports 32a, 42a are provided on the side periphery, and one (see FIG. 3) or both ends (see FIG. 4) of both ends in the optical path direction are opened, and the openings 32b, 42b are opened.
, 42c are formed.

In addition, when the open end 32b is formed only at one end in the optical path direction as shown in FIG. 3, it is recommended to provide the gas inlet 32a on the side periphery near the other end so that the gas is diffused throughout the cell. desirable. On the other hand, as shown in FIG.
2c are provided at both ends in the optical path direction, it is preferable to provide the gas inlet 42a at the center in the longitudinal direction of the cell. Although not shown, the sample gas introduced from the gas inlet ports 32a, 42a diffuses inside the cell, and the open ends 32b, 42b, 42.
Since the sample is discharged from c, the dead space g between the cell 32 and the detector 33, the dead space h between the light source 41 and the cell 42, and the dead space i between the cell 42 and the detector 43 are It will be filled with gas. Moreover, since the sample gas is naturally pressurized to above atmospheric pressure by the pump (it cannot be delivered unless it is pressurized), the dead spaces g to i are filled only with the sample gas, and atmospheric gas, etc. Infiltration of atmospheric gas is naturally prevented. By the way, since the choppers 34 and 44 are provided in g and h of the dead space, the chopper 34 is provided in the space g between the chopper 34 and the detector 33 and the space h' between the chopper 44 and the light source 41. , 44, it seems that the gas from the open ends 32b, 42b cannot reach the choppers 34, 44, but the choppers 34, 44 have holes 34a, 44 for light transmission.
Since one or more holes 44a are formed and the chopping frequency is high, such as one plate Z, the spaces g and h' are also provided with light transmission holes 34a and 44 of the chopper.
Gas is constantly sent to the sample through a, and the sample is filled with the gas. Therefore, all of the dead spaces g to i are filled with the sample gas, so that the light emitted from the light sources 31 and 41 is absorbed only by the sample gas, and the detectors 33 and
43, making it possible to perform highly accurate measurements unaffected by atmospheric gas.

Next, Figure 5 shows a double beam type infrared gas analyzer as another embodiment of the present invention. In this embodiment, not only the sample cell 51 but also the comparison cell 52 have both ends open. Open ends 52b and 52c are formed, and a pressurized comparison gas is always fed into the cell from a pump (not shown) through a gas inlet 52a. As a result, the open end 5
Since the dead spaces j and k between 2b and 52c and the light source 53 and detector 54 will be filled with the comparison gas,
The atmospheric gas is in the dead space 1 at both ends of the sample cell 51,
Intrusion is prevented not only into m but also into the dead spaces i and k. Therefore, according to the double beam type infrared gas analyzer having this configuration, highly accurate measurement can be performed with both optical paths being unaffected by atmospheric gas. The analyzers shown in the above examples all employ a method of intermittent light using a chopper, but there are also methods that do not use a chopper,
For example, it goes without saying that the present invention can be practiced in an analyzer that alternately introduces a comparison gas and a sample gas into two cells by switching a switching valve.

That is, the present invention is characterized by the structure of the cell, and configurations other than the cell (types of detectors, light sources, etc.) are not limitations of the present invention. As detailed above, the present invention provides a gas analyzer in which a light source, a cell through which the light emitted from the light source passes, and a detector that receives the light passing through the cell are arranged in series. A gas inlet is formed at a position that does not block the optical path of the cell, and at least one of both ends of the cell in the optical path direction is an open end, and pressurized gas is introduced into the cell from the gas inlet, Since the gas is made to flow out from the open end, the sample gas or reference gas introduced into the cell flows out from the open end while diffusing inside the cell, thereby preventing contact with the light source and/or detector. Since the dead space between them is filled with these gases, the intrusion of atmospheric gases can be effectively prevented.

Therefore, even if the atmospheric gas is the component gas to be measured or a gas having an absorption band similar to it, highly accurate measurement can be performed without being affected by it. This advantage in measurement accuracy is extremely noticeable when measuring low concentration gases using a short cell, and is equally noticeable when measuring gases that are contained in large amounts in the atmosphere, such as carbon dioxide. In addition, since the dead space is filled with the sample gas or comparison gas flowing inside the cell, it can be sealed with an O-ring,
Since there is no need to purge using a separate purge gas, the analyzer itself has structural advantages such as fewer parts, lower cost, and a simpler and more compact configuration.

[Brief Description of the Drawings] Figures 1 and 2 are overall configuration diagrams showing conventional analyzers, respectively, and Figures 3 to 5 are overall configuration diagrams showing each embodiment of the gas analyzer according to the present invention. It is. 31, 41, 53... light source, 32, 42, 51, 52...
...Cell, 33, 43, 54...Detector, 32a, 42a
, 52a... Gas inlet, 32b, 42b, 4
2c, 52b, 52c...Open end. Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Scope of Claims] 1. In a gas analyzer in which a light source, a cell through which light emitted from the light source passes, and a detector that receives the light passed through the cell are arranged in series, the optical path of the cell is blocked. A gas inlet is formed at a position that is not too far away, at least one of both ends in the optical path direction of the cell is an open end, pressurized gas is introduced into the cell from the gas inlet, and gas is introduced from the open end. A gas analyzer characterized in that the gas is allowed to flow out. 2. The gas analyzer according to claim 1, wherein each of the light source and the cell are of a single beam type.