JPS6140059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas analysis system in which a sample gas sampled by a probe is introduced into a gas analyzer through a first semipermeable membrane gas phase dehumidifier.

Generally, if the sample gas introduced into the gas analyzer contains moisture, the window of the reaction cell will be contaminated or span drift will occur, so it is desirable to remove as much moisture as possible from the sample gas. Among gas analyzers, especially in the case of an SO ₂ gas analyzer, SO ₂ gas easily dissolves in drain, so the moisture in the sample gas is removed using a dehumidifier, and the sample gas is removed from the probe that collects the sample gas. The gas pipe leading to the dehumidifier is heated to above the dew point of SO ₂ gas. However, as the distance between the probe and the dehumidifier increases, the power consumption for heating the conduit increases and it becomes difficult to provide uniform heating.

In order to operate a gas analyzer accurately and stably for a long period of time, it is necessary to pre-treat the sample gas to a clean state by removing dust, mist, and moisture with as little loss as possible before introducing it into the analyzer. It won't happen.

However, in order to reduce the loss in the pretreatment section, it is necessary to minimize the generation of condensed water, reduce the contact time between the condensed water and the sample gas, and so on.
Care must be taken to select materials for the parts that come into contact with the sample gas that do not react with the components to be analyzed.

On the other hand, in order for a semi-permeable membrane vapor phase dehumidifier to operate well, it is necessary to remove dust, mist, and moisture in advance.

Furthermore, if instrument air is not available as a dry purge gas for a vapor phase dehumidifier, it must be produced by the system itself.

An object of the present invention is to provide a gas analysis system equipped with an inexpensive and efficient sample gas dehumidifying means that reduces the complexity of maintenance and inspection as much as possible.

A further object of the present invention is to provide a gas analysis system that can prevent freezing accidents at the drain outlet in cold regions and does not require heating or keeping warm of the gas pipe between the probe and the dehumidifier. It is.

In order to achieve these objects, the present invention provides, in the gas analysis system mentioned at the beginning, an atmosphere-opening tube with one end open to the atmosphere, and the gas exhausted from the gas analyzer is exhausted into the atmosphere-opening tube. This exhausted exhaust gas is introduced as a dry purge gas into the first semipermeable membrane vapor phase dehumidifier through the second semipermeable membrane vapor phase dehumidifier, and A part of the sample gas before being introduced into the gas analyzer through the gas analyzer is branched and introduced into a conduit between the atmosphere open pipe and the second semipermeable membrane gas phase dehumidifier or into the atmosphere open pipe. This constitutes a gas analysis system characterized by the following.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

The sample gas is taken by probe 1,
After primary dust removal here, secondary dust removal is performed by a filter 2 provided as required. When the sample gas contains water, condensed water generated on the filter 2 is sucked together with the bypass gas by the air aspirator 15. If the filter 2 and the dehumidifier 3, which will be described later, are housed in a constant temperature bath 26 heated to a temperature higher than the dew point temperature of the sample gas, the condensed water will not be generated, and gas dissolution loss can be reduced. In addition, by bypassing and suctioning a part of the sample gas from the filter 2 by the air aspirator 15, a larger amount of sample gas is sucked into the filter 2 per unit time. By increasing the rate at which gas is replaced with new sample gas and by bypassing the sample gas sucked into the filter from near the outer peripheral surface of the filter base, the situation where old sample gas accumulates in the filter is avoided. I can do it. The air aspirator 15 does not require a large suction force, and preferably has a structure in which the suction force does not change even if dust or drainage is mixed in. The condensed water sucked in by this is diluted with air and discharged in a state close to a gas phase, so there is no fear that the discharge port will freeze and become clogged.

The sample gas that has passed through the filter 2 is dehumidified by a first semipermeable membrane gas phase dehumidifier 3 until the outlet gas dew point becomes below the outside air temperature, and is further dehumidified by a pump 4, a second filter 5 for tertiary dust removal, and a flow meter. 6 and is introduced into a gas analyzer 7. A portion of the gas is bypassed and exhausted on the outlet side of the pump 4 to speed up the response.

The exhaust gas from the gas analyzer 7 passes through a conduit 21,
As shown in FIG. 2, the air is exhausted into the atmosphere opening tube 8 through an introduction 82 formed at the other end of the atmosphere opening tube 8, which has an open end 81 opening to the atmosphere at one end. The internal exhaust gas is taken out from an outlet 83 formed in the middle of the atmosphere opening pipe 8, and filtered through the filter 9 (first
Figure). In addition, the inlet port 82 and the outlet port 83
A second inlet 84 is also shown between the two, which will be explained later in conjunction with the embodiment of FIG.

The exhaust gas from the filter 9 is dehumidified by the pump 10 in the second semi-permeable membrane gas phase dehumidifier 11 together with the gas bypassed on the outlet side of the pump 4 and guided through the flow meter 16, and then It is used as a dry purge gas for the gas phase dehumidifier 3. The shortage of exhaust gas and bypass gas used as dry purge gas is made up for by taking in atmospheric air from the atmospheric opening pipe 8. This dry purge gas is pressurized to about 0.5 to 1 kg/cm ² by the pump 10 and introduced into the vapor phase dehumidifier 11, and a part of the dry gas taken out from the outlet conduit 22 is brought to atmospheric pressure by the needle valve 14. After that, it is returned through the conduit 24 as a dry purge gas for the dehumidifier 11 itself.

The other part of the dry gas taken out from the gas phase dehumidifier 11 via the conduit 22 is reduced to atmospheric pressure by the capillary fixed restrictor 12, and then transferred to the conduit 23 containing the flow meter 13.
The gas is guided through the gas phase dehumidifier 3 and used as a dry purge gas. Since a pressure difference proportional to the flow rate occurs at both ends of the fixed throttle 12, the gas pressure in the conduit 22 can be determined from the indication from the flow meter 13, and a pressure gauge can be omitted.

Here, the reason why the sample gas discharged from the analyzer 7 is passed through the atmosphere opening tube 8 will be explained in more detail.

As mentioned above, an infrared analyzer is often used as the analyzer 7. This infrared radiation analyzer utilizes the fact that molecules with a dipole moment absorb infrared rays at wavelengths unique to each molecule, creating a transition between their vibrational energy levels.
The concentration of the sample gas is determined by introducing the sample gas into a measurement cell of a certain length and measuring the attenuation rate of the infrared rays that pass through the measurement cell at wavelengths that are absorbed by the molecules whose concentration in the sample gas is to be measured. It enables measurement.

For this purpose, the gas pressure in the measuring cell is, for example, 2
When it doubles, the density of molecules within it also doubles, and as a result, the measured concentration also doubles.

Therefore, in order to perform accurate concentration measurements, it is necessary to maintain the gas pressure within the measurement cell constant. However, when the analyzer 7 is directly connected to the gas phase dehumidifier 3 in order to obtain the purge gas from the gas phase dehumidifier 3 from the gas analyzer 7, the analyzer 7
The gas pressure inside the measurement cell may fluctuate, making it impossible to expect accurate concentration measurements.

Therefore, by using the atmosphere opening tube 8, the gas pressure within the measurement cell is maintained at a constant pressure of approximately atmospheric pressure, thereby ensuring the accuracy of the concentration measurement in the analyzer 7.

FIG. 3 shows the detailed structure of the semipermeable membrane type gas phase dehumidifiers 3 and 11. This vapor phase dehumidifier is constructed by supporting a large number of inner tubes 30 inside an outer tube 27 via partition plates 28 and 29. Each inner tube 30
For example, it is composed of EI DuPont's product name NAFION, and has the function of selectively transmitting only water vapor. Therefore, when a sample gas containing water vapor, that is, a wet sample gas, is introduced into each inner tube 30 from the inlet 31 and discharged from the outlet 32, the water vapor in the sample gas flows into each inner tube 30 in the process. The water is discharged into the outer tube 27 through the evacuator. On the other hand, the outer tube 27
When dry purge gas is allowed to flow from the purge gas inlet 33 to the outlet 34, water vapor in the sample gas discharged into the outer tube 27 is absorbed by the dry purge gas introduced from the inlet 33, and
It will be discharged as wet purge gas. In this way, a dry gas free of water vapor can be obtained from the outlet 32.

The capillary fixed restrictor 12 in FIG. 1 is replaced with a needle valve 18 as shown in FIG.
It is clear from the functional point of view that a pressure gauge 17 may be provided in order to know the gas pressure of the gas.
Further, in order to check the performance of the gas phase dehumidifier 11 for dehumidifying the purge gas of the gas phase dehumidifier 3, a flow meter 19 may be provided in the conduit 24 in addition to the pressure gauge 17.

FIG. 5 shows another modified embodiment of the embodiment shown in FIG. In this embodiment, in order to improve the performance of the gas phase dehumidifier 3, the wet purge gas is sucked by the air aspirator 20, and the drain and bypass gas from the filter 2, which requires relatively weak suction force, are also sucked. Common air aspirator 20 via capillary fixed throttle 17
This is what I try to do.

FIG. 6 shows that it is also possible to omit the filter 2 (see FIG. 1) and send the sample gas sampled by the probe 1 directly to the vapor phase dehumidifier 3. In some cases, an NH ₃ converter or the like may be inserted between the probe 1 and the gas phase dehumidifier 3.

FIG. 7 shows an embodiment in which the filter 2 is omitted and the wet purge gas from the vapor phase dehumidifier 3 is sucked by an air aspirator 20. It is clear that this embodiment can also be implemented within the spirit of the invention.

FIG. 8 shows an embodiment in which a bypass gas conduit 25 branched from the outlet side of the pump 4 and for speeding up the response is connected to the second inlet 84 of the atmosphere opening pipe 8 (see FIG. 2). be. With this configuration as well, the same effect as in the case of FIG. 1 can be performed.

As described above, according to the present invention, in a gas analysis system having a semipermeable membrane gas phase dehumidifier immediately after the probe, in order to obtain the dry purge gas,
A part of the sample gas at the inlet of the gas analyzer is used by bypass, and the exhaust gas from the gas analyzer is also used, and these gases are passed through the second semi-permeable membrane gas phase dehumidifier. Although the cost is low and maintenance and inspection are less complicated, the dehumidification effect of the sample gas can be significantly improved, and the outlet side of the gas analyzer is connected to the atmosphere opening pipe, allowing exhaust gas to be passed through the dry purge gas inlet. Therefore, the dehumidified exhaust gas can be used effectively without affecting the indications of the gas analyzer. By installing a dehumidifier immediately after the probe, condensed water will not be generated inside the analytical instrument panel.
There is no need for a special dehumidifier inside the panel.

Additionally, the system of the present invention does not require any special instrumentation gas because the system generates its own dehumidifier purge gas.

The dehumidifying capacity of a semipermeable membrane vapor phase dehumidifier depends on its ambient temperature; as the ambient temperature decreases, the dehumidifying capacity increases and the outlet gas dew point decreases. Therefore, it is necessary to expose the sample gas outlet side of the dehumidifier 3 to the outside air temperature, and by doing so, the outlet gas dew point slides up and down with the outside air temperature, achieving the purpose of eliminating the need for heating the gas conduit. .

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing an example of a pipe open to the atmosphere, FIG. 3 is a vertical cross-sectional view showing an example of a semipermeable membrane type vapor phase dehumidifier, and FIG. 4 is a system diagram showing another embodiment of the present invention, FIG. 5 is a system diagram showing still another embodiment of the present invention, and FIGS. 6, 7, and 8 are diagrams showing still other embodiments of the present invention, respectively. FIG. 2 is a system diagram of main parts of the embodiment. 1... Probe, 3... First semipermeable membrane gas phase dehumidifier, 4, 10... Pump, 7... Gas analyzer,
8...Air open pipe, 11...Second semipermeable membrane gas phase dehumidifier, 12...Capillary fixed throttle, 25...Bypass conduit.

Claims (1)

[Claims] 1. A gas analysis system in which a sample gas sampled by a probe is introduced into a gas analyzer through a first semipermeable membrane gas phase dehumidifier,
An air-opening tube with one end open to the atmosphere is provided, the gas discharged from the gas analyzer is exhausted into the air-opening tube, and the exhausted exhaust gas is passed through a second semipermeable membrane gas phase dehumidifier. A part of the sample gas is introduced into the first semipermeable membrane gas phase dehumidifier as a dry purge gas, and a part of the sample gas before being introduced into the gas analyzer through the first semipermeable membrane gas phase dehumidifier. A gas analysis system characterized in that the gas is branched and introduced into a conduit between the atmosphere open pipe and the second semipermeable membrane gas phase dehumidifier or into the atmosphere open pipe. 2. In the gas analysis system according to claim 1, the second semipermeable membrane gas phase dehumidifier and the first
A gas analysis system characterized in that a flow meter and a capillary fixed throttle are arranged in a conduit between a dry purge gas inlet of a semipermeable membrane gas phase dehumidifier. 3. In the gas analysis system according to claim 1, the second semipermeable membrane gas phase dehumidifier and the first
A gas analysis system characterized in that a flow meter, a needle valve, and a pressure gauge are arranged in a conduit between a dry purge gas inlet of a semipermeable membrane gas phase dehumidifier. 4. The gas analysis system according to any one of claims 1 to 3, characterized in that the wet purge gas of the first semipermeable membrane gas phase dehumidifier is sucked by an air aspirator. gas analysis system.