JPS6140058B2 - - 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 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 the gas analysis system described at the beginning with an atmosphere-opening pipe with one end open to the atmosphere, and the sample gas is collected before being introduced into the gas analyzer through the gas-phase dehumidifier. A gas analysis system comprising: branching off a part of the air to exhaust it into the air-opening pipe from the other end, and introducing the gas in the air-opening pipe into the vapor phase dehumidifier as a dry charge gas. It is.

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 a probe 1, where it is cleared of coarse dust before entering an optionally provided filter 2. Condensed water generated on the filter 2 when the sample gas contains water is sucked together with the bypass gas by the first air aspirator 12. Here, if the filter 2 and the dehumidifier 3 described later are housed in a constant temperature bath 30 heated to a temperature higher than the dew point temperature of the sample gas, the above-mentioned condensed water will not be generated, and gas dissolution loss can be reduced. . Also, air aspirator 1
By bypassing a part of the sample gas from the filter 2 and sucking it in by the filter 2, a larger amount of sample gas is sucked into the filter 2 per unit time, so that the sample gas in the filter 2 becomes a new sample. By increasing the rate of gas replacement 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 first air aspirator 12 does not require a large suction force,
It is desirable to have a structure in which the suction power does not change even if dust or drainage gets 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 semipermeable membrane gas phase dehumidifier 3 until the outlet gas dew point becomes below the outside air temperature, and then introduced into a gas analyzer 7 through a pump 4, a filter 5, and a flow meter 6. be done.

The gas outlet of the gas analyzer 7 is connected via a conduit 21 to the middle of an atmosphere open tube 8 whose one end is open to the atmosphere in order to reduce indication errors due to changes in sample gas pressure within the analyzer. A portion of the sample gas branched and taken out from the outlet side of the pump 4, that is, a bypass gas, is introduced through a flow meter 17 into the end of the air release pipe 8 opposite to the open end. The gas in the atmosphere opening pipe 8 is guided as a dry purge gas to the dry purge gas inlet of the vapor phase dehumidifier 3 through a conduit 22 having a flow meter 9, a needle valve 10 for reducing the pressure to atmospheric pressure, and a pressure gauge 11. The purge gas that has absorbed moisture in the vapor phase dehumidifier 3, that is, the wet purge gas, is sucked by the second air aspirator 13. Note that the second air aspirator 13 is made to generate a high vacuum. Both air aspirators 12, 13 perform the desired suction action with the aid of compressed air.

FIG. 2 shows the detailed structure of the atmosphere opening pipe 8. As shown in FIG. A part of the sample gas passes through the gas phase dehumidifier 3 and the pump 4 before being introduced into the gas analyzer, and is branched from there and passes through the flow meter 17 to the atmosphere release pipe 8.
It is introduced into the atmosphere open tube 8 from an inlet 82 on the opposite side to the open end 81 of the tube. Exhaust gas from the gas analyzer 7 is discharged via a conduit 21 to an atmosphere open pipe 8.
Exhaust gas inlet 83 provided in the middle part of the
introduced through. Dry purge gas for the gas phase dehumidifier 3 is taken out from an outlet 84 provided between both inlets 82 and 83.

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.

Therefore, if the gas pressure within the measurement cell doubles, for example, the molecular density therein also doubles, and as a result, the measured concentration value 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 barge 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 dehumidifier 3. This vapor phase dehumidifier 3 has a large number of inner tubes 34 arranged inside an outer tube 31 via partition plates 32 and 33.
It is based on the support of Each inner tube 34 is made of, for example, NAFION, a product of EI DuPont, and has a function of selectively transmitting water vapor. Therefore, a sample gas containing water vapor, that is, a wet sample gas, is introduced into each inner tube 34 from the inlet 35,
When discharged from the outlet 36, the water vapor in the sample gas is discharged into the outer tube 31 through the tube wall of each inner tube 34 in the process. On the other hand, if the dry purge gas led from the atmosphere open tube 8 is allowed to flow from the barge gas inlet 37 to the outlet 38 of the outer tube 31, the water vapor in the sample gas discharged into the outer tube 31 will be introduced from the inlet 37. It is absorbed by the dry purge gas and is discharged from the outlet 38 as wet purge gas. In this way, a dry sample gas containing no water vapor can be obtained from the outlet 36.

FIG. 4 shows an embodiment in which a capillary fixed throttle 14 is provided in place of the needle valve 10 shown in FIG. According to this configuration, the purge side pressure of the dehumidifier 3 can be determined from the indication of the flow meter 9 by utilizing the fact that the flow rate and the pressure difference between both ends of the fixed throttle 14 are almost proportional. The pressure gauge 11 can be omitted.

Fig. 5 shows that by inserting a capillary fixed throttle 15 on the side of the filter 2, which has a weak suction force, it is possible to suction the wet purge gas from the vapor phase dehumidifier 3, and to suction the condensed water and bypass gas from the filter 2. This shows an embodiment in which a common air aspirator 16 is used for both the air and air aspirators.

As described above, according to the present invention, by connecting the outlet side of the gas analyzer and the sample gas outlet side of the gas phase dehumidifier to the atmosphere open pipe,
Part of the dry analyzer exhaust gas and sample gas can be used as dry purge gas for a vapor phase dehumidifier without affecting the gas analyzer's readings. By suctioning with a highly durable air aspirator, there is no need for complicated work such as periodic replacement of the diaphragm or valve in a diaphragm suction device, and there is little need for maintenance or inspection, so-called maintenance. It can be a free system. Furthermore, by providing a dehumidifier immediately after the probe, no condensed water is generated within the analytical instrument panel, so there is no need for a special dehumidifier within the panel.

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 details of the atmosphere opening pipe in Fig. 1, and Fig.
This figure is a longitudinal cross-sectional view showing details of the semipermeable membrane type vapor phase dehumidifier shown in FIG. 1, and FIGS. 4 and 5 are system diagrams of essential parts showing other embodiments of the present invention, respectively. 1... Probe, 3... Semi-permeable membrane gas phase dehumidifier,
4...Pump, 6,9...Flowmeter, 7...Gas analyzer, 8...Atmospheric release pipe, 10...Needle valve,
11...Pressure gauge, 12, 13, 16...Air aspirator, 14...Capillary fixed throttle.

Claims (1)

[Claims] 1. In a gas analysis system in which a sample gas is introduced into a gas analyzer through a semi-permeable membrane gas phase dehumidifier, an atmosphere open pipe with one end open to the atmosphere is provided, and the sample gas is introduced into the gas analyzer through the gas phase dehumidifier. A part of the sample gas before being introduced into the atmosphere is branched and exhausted from the other end into the atmosphere-opening tube, and the gas in the atmosphere-opening tube is introduced into the vapor phase dehumidifier as a dry purge gas. gas analysis system.