JPS6035870Y2 - gas analyzer - Google Patents

Description

[Detailed description of the invention] The present invention introduces a sample gas collected by a probe into a gas analyzer through a semipermeable membrane gas phase dehumidifier, and passes through the semipermeable membrane gas phase dehumidifier to analyze the gas. The present invention relates to a gas analyzer in which a part of the sample gas before being introduced into the analyzer is branched and introduced as a dry purge gas into the 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 SO2 gas analyzer, SO2 gas easily dissolves in drain, so the moisture in the sample gas is removed by a dehumidifier, and the sample gas is removed from the probe that collects the sample gas to the dehumidifier. All the gas conduits are heated above the dew point of the SO□ gas.

However, when 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. No.

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 use the material of the part that comes into contact with the sample gas as the target component. Care must be taken to select a material that does not react with

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 semipermeable membrane gas phase dehumidifier, it must be produced by the system itself.

It would be convenient if the dried spent gas discharged from the gas analyzer could be used as the dry purge gas for a semipermeable membrane gas phase dehumidifier, but if a chemiluminescent gas analyzer is used, for example, It is not preferable to use exhaust gas as dry purge gas for a semipermeable membrane gas phase dehumidifier.

In other words, in a chemiluminescent gas analyzer, in order to measure, for example, the concentration of nitric oxide (No) in a sample gas, the nitric oxide and ozone are chemically reacted, and the intensity of the emitted light is determined by the chemical reaction of the nitric oxide and ozone. To measure the No concentration,
This is because it is unavoidable that excess ozone is included in the exhaust gas from the gas analyzer.

This ozone is a so-called aggressive and harmful gas that has a strong tendency to corrode materials it comes in contact with.

Furthermore, if the exhaust gas contains nitrogen oxides, nitric acid is produced by the nitrogen oxides, moisture and ozone, and if the exhaust gas contains sulfur oxides, Sulfuric acid is produced by the sulfur oxides, moisture and ozone.

These nitric acids and sulfuric acids are also highly aggressive, and therefore, along with the aforementioned ozone, they corrode the semipermeable membrane tube of a vapor phase dehumidifier, so eventually the exhaust gas from the gas analyzer must be replaced with a semipermeable membrane tube. It is not preferable to use it as a dry purge gas in a phase dehumidifier.

An object of the present invention is to provide a gas analyzer equipped with a sample gas dehumidifying means that is inexpensive and efficient, requiring as little maintenance and inspection as possible.

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

According to the present invention, in the gas analyzer mentioned at the beginning, a pump and a second semipermeable membrane gas phase dehumidifier are connected to the conduit leading dry purge gas to the first semipermeable membrane gas phase dehumidifier. In addition, the inlet side of the pump is connected to a branch pipe whose one end communicates with the atmosphere through a filter so that air from the atmosphere can be sucked in.

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

FIG. 1 shows an embodiment of the present invention.

A sample gas is collected by a probe 1, and after primary dust removal there, a filter 2 is provided as necessary.
Secondary dust removal is performed.

If the sample gas contains water, the condensed water generated on the filter 2 is sucked together with the bypass gas by an air aspirator 15 operated with the aid of compressed air.

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 replaced with new sample gas. 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;
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 the first semipermeable membrane gas phase dehumidifier 3 until the outlet gas dew point becomes below the outside air temperature, and then passes through the pump 4, the tertiary dust removal filter 5, and the flow meter 6, and then the gas is dehumidified. It is introduced into the analyzer 7.

Note that if the sample gas is at high pressure, the pump 4 may be omitted.

A portion of the dehumidified sample gas obtained from the outlet side of the pump 4 is branched from there via a branch conduit 25 containing a flow meter 16 and a second pump 10 to a second semipermeable membrane vapor phase dehumidifier. It is introduced into the container 11.

A part of the dry gas dehumidified in the second semi-permeable membrane vapor phase dehumidifier 11 and taken out through the conduit 22 is used as its own dry purge gas by being introduced through the conduit 24 containing the needle valve 14, and the other part is used as its own dry purge gas. A part of the first semipermeable membrane vapor phase dehumidifier 3
Used as a dry purge gas.

Since only a part of the sample gas obtained through the flow meter 16 as this dry purge gas is insufficient, the shortage is made up for by accepting a decrease in efficiency due to the contamination of some moisture, dust, etc. 8 to the suction side of the pump 10.

The gas phase dehumidifier 11 has a pump 10 with a pressure of 0.5 to 1.0
Gas pressurized to about kg/cIt is introduced into the dehumidifier 11.
The own dry purge gas is returned to atmospheric pressure using the needle valve 14.

A portion of the dry gas taken out from the gas phase dehumidifier 11 is reduced in pressure to atmospheric pressure by a capillary fixed throttle 12 and then passed through a conduit 23 including a flow meter 13 to the first semipermeable membrane 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 on the outlet side of the gas phase dehumidifier 11 can be determined from the indication from the flow meter 13, 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.

FIG. 2 shows the detailed structure of the semipermeable membrane type gas phase dehumidifiers 3 and 11.

This vapor phase dehumidifier has partition plates 28 and 39 inside the outer pipe 27.
A large number of inner tubes 30 are supported through the tubes.

Each inner tube 30 is made of, for example, NAFION, a product of EI DuPont, and has a function of selectively transmitting only water vapor.

Therefore, when a sample gas containing water vapor, that is, a wet sample gas, is introduced from the inlet 31 into each inner tube 30 and discharged from the outlet 32, the water vapor in the sample gas passes through the wall of each inner tube 30 and enters the outer tube 27. discharged inside.

On the other hand, if the dry purge gas is allowed to flow from the purge gas port 33 of the outer tube 27 toward the outlet 34, the 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 the water vapor will be absorbed by the dry purge gas introduced from the inlet 33. 34 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 shown in FIG. 1 may be replaced with a needle valve 18 as shown in FIG. 3, and the conduit 22 may be provided with a pressure gauge 17 for determining the gas pressure.

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. 4 shows that the filter 2 can be omitted and the sample gas sampled by the probe 1 can be sent directly to the gas phase dehumidifier 3.

In some cases, between the probe 1 and the vapor phase dehumidifier 3, N
It is also possible to insert an H3 converter or the like.

Furthermore, FIG. 5 shows that the wet purge gas of the semipermeable membrane gas phase dehumidifier 3 is actively sucked by the air aspirator 20 to improve the dehumidification efficiency, and at the same time, for the filter 2 which has a smaller suction force. This shows an embodiment in which a relatively powerful air aspirator 20 is also used for suctioning the condensed water of the filter 2 and the bypass by interposing a capillary fixed throttle 21.

As described above, according to the present invention, in a gas analyzer having a semipermeable membrane type gas phase dehumidifier immediately after the probe, in order to obtain the dry purge gas, the dry sample gas output from the dehumidifier itself is used as much as possible. By branching out some of the air and using it preferentially, and using atmospheric air to make up for the shortage, it is cheaper and reduces the complexity of maintenance and inspection.
The dehumidification effect of sample gas can be significantly improved.

Further, by providing a dehumidifier immediately after the probe, no condensed water is generated within the branch instrument panel, so there is no need for a special dehumidifier within the panel.

Furthermore, since the device of the present invention generates the dehumidifier purge gas by itself, no special instrumentation gas is required.

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 layout diagram of one embodiment of the present invention, Fig. 2 is a vertical sectional view showing an example of a semipermeable membrane vapor phase dehumidifier, and Fig. 3 is a system layout diagram of another embodiment of the invention. , FIG. 4 is a system layout diagram of the main parts of a further different embodiment of the present invention, and FIG. 5 is a system layout diagram of still another embodiment of the present invention. 1... Probe, 3... First semi-permeable membrane gas phase dehumidifier, 7... Gas analyzer, 8...
...Atmosphere communication branch pipe, 11...Second semipermeable membrane gas phase dehumidifier, 12...Capillary fixed throttle, 14.
18... Needle valve, 25... Branch pipe.

Claims (4)

[Scope of utility model registration request] (1) The sample gas collected by the probe is
A part of the sample gas is introduced into the gas analyzer through the semipermeable membrane gas phase dehumidifier, and a part of the sample gas is branched before being introduced into the gas analyzer through the first semipermeable membrane gas phase dehumidifier. In the gas analyzer, the dry purge gas is introduced into the first semipermeable membrane gas phase dehumidifier as a dry purge gas, and a pump and a second A semipermeable membrane gas phase dehumidifier is installed, and a branch pipe with one end communicating with the atmosphere is provided on the inlet side of the pump so that air from the atmosphere can be taken in.
A gas analyzer characterized in that it is connected via a filter. (2) Scope of Utility Model Registration In the gas analyzer according to claim 1, the connection between the second semipermeable membrane gas phase dehumidifier and the dry purge gas inlet of the first semipermeable membrane gas phase dehumidifier A gas analyzer characterized in that a capillary fixed restrictor and a flow meter are arranged in a conduit between the two. (3) Scope of Utility Model Registration In the gas analyzer according to claim 1, the second semipermeable membrane gas phase dehumidifier and the dry purge gas inlet of the first semipermeable membrane gas phase dehumidifier A gas analyzer characterized in that a pressure gauge, a needle valve, and a flow meter are arranged in a conduit between the two. (4) In the gas analyzer according to any one of claims 1 to 3 of the utility model registration claim, the wet purge gas of the first semipermeable membrane gas phase dehumidifier is sucked out by an air aspirator. Characteristic gas analyzer.