JPS6140060B2 - - 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 water 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, power consumption for heating the conduit increases and it becomes difficult to provide uniform heating.

In order for a gas analyzer to operate accurately and stably for a long period of time, dust, mist, and moisture must be pretreated to a clean state with minimal loss of sample gas before introduction 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 gas analysis system is configured such that the exhausted sample gas is introduced as a dry purge gas into the first semipermeable membrane gas phase dehumidifier through a second semipermeable membrane gas phase dehumidifier. be.

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

FIG. 1 shows an embodiment of the present invention.
A sample gas is sampled by a probe 1, and after being subjected to primary dust removal there, it is subjected to secondary dust removal by a filter 2 provided as required. When the sample gas contains moisture, the condensed water generated on the filter 2 is transferred to the air aspirator 1 along with the bypass gas.
It is attracted by 5. 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 by the air aspirator 15, a larger amount of sample gas is sucked into the filter 2 per unit time, so that the sample gas in the filter 2 is fresh. By increasing the speed at which the sample gas is replaced with the sample gas and by bypassing the sample gas sucked into the filter from near the outer peripheral surface of the filter base, it is possible to avoid a situation where old sample gas accumulates in the filter. 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 the first semipermeable membrane gas phase dehumidifier 3 until the outlet gas dew point becomes below the outside temperature, and then passes through the pump 4, the tertiary dust removal filter 5, and the flow meter 6. The gas is introduced into a gas analyzer 7. Note that if the sample gas is at high pressure, the pump 4 may be omitted.

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 inlet 82 formed at the other end of the atmosphere opening tube 8, which has an open end 81 with one end open to the atmosphere. The exhaust gas exhausted into the atmosphere opening pipe 8 is taken out from the outlet 83, filtered through the filter 9 and pump 10.
The air is introduced into the second semipermeable membrane gas phase dehumidifier 11 through the air. A part of the dry gas dehumidified by this second semipermeable membrane gas phase dehumidifier 11 and taken out via the outlet conduit 22 is used as a dry purge gas for the dehumidifier 11 itself, and the other part is It is used as a dry purge gas for the dehumidifier 3. The shortage of the exhaust gas used as the dry purge gas is made up by taking in the atmosphere from the atmosphere opening pipe 8. This dry purge gas is 0.5 to 1
It is pressurized to about Kg/cm ² and introduced into the vapor phase dehumidifier 11.
A portion of the dry gas taken out from the conduit 22 is returned to atmospheric pressure by the needle valve 14 and then returned via the conduit 24 as 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.
It is led to the first gas phase dehumidifier 3 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 flow meter 1
The gas pressure in the conduit 22 can be determined from the instruction No. 3, and the pressure gauge can be omitted. In the above configuration, the pump 10 may be disposed on the wet purge gas suction side of the first gas phase dehumidifier 3.

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 analyzer utilizes the fact that molecules with dipole moments absorb infrared rays at wavelengths unique to each molecule, creating a transition between their vibrational energy levels.
The sample gas is guided into a measurement cell of a certain length,
Concentration measurement is made possible by measuring the attenuation rate of infrared rays transmitted through the measurement cell at wavelengths that are absorbed by molecules whose concentration in the sample gas is to be measured.

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 at a constant level. However, in order to obtain purge gas for the gas phase dehumidifier 3 from the gas analyzer 7, the gas phase dehumidifier 3
If the analyzer 7 is directly connected to the analyzer 7, the gas pressure within the measurement cell of the analyzer 7 may fluctuate, and accurate concentration measurement cannot be expected.

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 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 sampling gas flows onto the wall of each inner tube 30. It is discharged into the outer tube 27 through the tube. On the other hand, if dry purge gas is allowed to flow from the purge gas inlet 33 to the outlet 34 of the outer tube 27, water vapor in the sample gas discharged into the outer tube 27 will be absorbed by the dry purge gas introduced from the inlet 33, and 34 as wet purge gas. In this way, a dry sample gas or 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.
A pressure gauge 16 may be provided to determine the gas pressure. Further, in order to confirm the performance of the gas phase dehumidifier 11 for dehumidifying the purge gas of the gas phase dehumidifier 3, a flow meter 17 may be provided in the conduit 24 in addition to the pressure gauge 16.

In FIG. 5, the filter 2 is omitted and the probe 1 is
This shows that it is also possible to directly feed the sample gas collected in the gas 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.

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,
The exhaust gas from the gas analyzer is used, and the exhaust gas is
I decided to pass it through a semi-permeable membrane gas phase dehumidifier.
Although the cost is low and the complexity of maintenance and inspection is reduced, the dehumidification effect of the sample gas can be significantly improved, and the outlet side of the gas analyzer can be connected to the atmosphere opening pipe to convert the exhaust gas into a dry purge gas. Therefore, the dehumidified exhaust gas can be effectively used without affecting the indications of the gas analyzer. By providing a dehumidifier immediately after the probe, no condensed water will be generated within the analytical instrument panel, so there is no need for a special dehumidifier within the panel.

Additionally, the system of the present invention does not require special instrumentation gases since the system produces its own dehumidifier purge gum.

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, the sample gas outlet side of the dehumidifier 3 needs to be exposed to the outside temperature, and by doing so, the output gas dew point will slide up and down with the outside temperature, achieving the purpose of eliminating the need to heat 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 an atmosphere-opening pipe, FIG. 3 is a vertical cross-sectional view showing an example of a semipermeable membrane gas phase dehumidifier, and FIG. FIG. 4 is a system diagram of another embodiment of the present invention, and FIG. 5 is a system diagram of main parts of still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Probe, 3... First semi-permeable membrane gas phase dehumidifier, 7... Gas analyzer, 8... Atmospheric open tube, 1
0... Pump, 11... Second semi-permeable membrane gas phase dehumidifier, 12... Capillary fixed throttle, 14, 18... Needle valve.

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 atmosphere-opening tube with one end open to the atmosphere is provided, and the gas discharged from the gas analyzer is exhausted into the atmosphere-opening tube, and the exhausted sample gas is passed through the second semipermeable membrane gas phase dehumidifier. A gas analysis system characterized in that it is introduced as a dry purge gas into the semi-permeable membrane type gas phase dehumidifier of item 1. 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.