JPS6035877Y2 - gas analyzer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a gas dehumidification system in a gas analyzer.

Depending on the gas analyzer, the moisture content in the gas may appear as an error in the analytical concentration indication value.

For example, infrared gas analyzers utilize the fact that molecules with dipole moments absorb infrared rays at wavelengths unique to each molecule, creating transitions between their vibrational energy levels. The concentration can be measured by introducing a sample gas into the sample cell and measuring the attenuation rate of the infrared rays transmitted through the sample cell at a wavelength that is absorbed by the molecules whose concentration is to be measured in the sample gas.

However, if water is contained in the sample gas, water has the property of absorbing infrared rays over a relatively wide range of wavelengths, so the infrared wavelength absorbed by the molecule whose concentration in the sample gas is to be measured and the absorption by the water are different. In this case, even if the attenuation rate of the infrared rays at that wavelength is measured, a measured concentration value containing an error corresponding to the amount absorbed by moisture will be obtained.

Therefore, it is desirable to remove as much moisture as possible from the sample gas.

However, in general infrared gas analyzers, in order to increase the stability of operation, a reference cell is installed separately from the sample cell, which is filled with a gas that does not absorb infrared rays (such as nitrogen) as a reference gas, and both the sample and reference cells are A method is used to measure the difference in transmitted light.

Therefore, in this method, if the water content in both the sample gas and the reference gas is made equal, errors due to water content cancel each other out, so no error occurs in the concentration measurement value.

To explain a specific example, infrared ammonia gas (NH3
) In the case of an analyzer, NH3 in the sample gas is converted to nitric oxide (NO) using a thermal converter, and the sum of the NO originally present in the sample gas and the converted NO is calculated as the first
The sample gas still containing NH3 is passed through a second infrared absorption cell, and the NH3 concentration in the sample gas can be determined from the difference in the amount of infrared absorption by both cells.

In this case, if the moisture content of each gas passed through the first cell and the second cell is made equal, the measured NH3 concentration will not include an error due to moisture.

Gas dehumidifiers are used in connection with gas analyzers in this manner, and such dehumidifiers include those using electronic gas coolers of cooling dehumidification type and semipermeable membrane vapor phase dehumidifiers that do not. There is.

In the former case, the dew point temperature of the gas at the outlet of the dehumidifier is set to 1 to
It is controlled at 3 degrees Celsius, and it is impossible to lower the dew point temperature any further due to freezing.

On the other hand, in the latter semipermeable membrane vapor phase dehumidifier, the dew point temperature is 120
It is possible to dehumidify relatively easily to temperatures equivalent to °C.

If the degree of dehumidification is low and the sample gas contains a large amount of water, the optical system will become more contaminated, causing zero drift in the indicator, and In the case of a chemiluminescent analyzer, span drift occurs in a similar manner, which prevents accurate analysis value indication.

Therefore, it can be said that a semipermeable membrane vapor phase dehumidifier with a high dehumidifying capacity is superior to an electronic gas cooler with a poor dehumidifying capacity.

FIG. 1 is a sectional view of such a semipermeable membrane vapor phase dehumidifier, and FIG. 1A is a sectional view taken along line XX' in FIG. 1.

See these figures.

The semipermeable membrane vapor phase dehumidifier includes an outer tube 1 and a number of inner tubes 3 supported inside the outer tube 1 via partition plates 2, 2. 3.3
Each inner tube 3 is made of a compound called NAFION, a trade name of EI DuPont, and has the function of selectively permeating water vapor from the inside to the outside through the tube wall. There is.

Now, while introducing the wet sample gas containing water vapor into each inner tube 3 from the inlet 4 and discharging it from the outlet 5, dry gas for purging is introduced from the other inlet 6 toward the output lower outside of the inner tube 3. , the water vapor in the wet sample gas passes through the wall of the inner tube 3 and is purged to the outside.

A semipermeable membrane gas phase dehumidifier has the above-described configuration and functions, and an example of the configuration of a conventional infrared gas analyzer using such a dehumidifier is shown in FIG.

Refer to the same figure.

The reference gas sampled by the probe 8 for sampling the reference gas passes through the gas flow path 16 and is removed by the filter 9.

A drain pot 15 is also provided in case drain occurs due to a drop in gas temperature.

The reference gas from which dust has been removed by the filter 9 is pressurized by the pump 10 and passed through the inner pipe of the semipermeable membrane vapor phase dehumidifier 11, and then controlled to a constant flow rate by the needle valve material flowmeter 12.
After further dust removal in the filter 13, the gas enters the reference cell 14A in the infrared gas analyzer 14, and the gas exiting there passes through the outside of the inner tube of the semipermeable membrane vapor phase dehumidifier 11 as a dry purge gas and is sent from the gas outlet. Dissipated into the atmosphere.

The reference gas introduced into the inner pipe of the dehumidifier 11 is supplied by the pump 10.
Although the partial pressure of water vapor is high because it is pressurized and compressed by Since the water vapor partial pressure is low, it can serve as a dry gas for purging.

In exactly the same way, the sample gas collected by the probe 8a passes through the filter 9a, is pressurized by the pump 10a, passes through the inner tube of the dehumidifier 11a, passes through the flowmeter 12a1 and the filter 13a, and is then sent to the infrared gas analyzer 14. The gas entering the inner sample cell 14B and exiting there passes through the outside of the inner tube of the dehumidifier 11a and is dissipated to the atmosphere from the gas outlet.

In the infrared gas analyzer 14, a reference cell 14A and a sample cell 14B are arranged spatially in parallel, and a chopper 14E driven by a motor (not shown) is arranged in front of them. ,14D
The structure is such that both cells 14A and 14B are alternately irradiated with infrared wavelength light from the cell.

A detector 14F is arranged behind both cells 14A and 14B to detect the difference in the amount of infrared absorption in both cells, and the concentration of the sample gas is measured by this (infrared gas Since the configuration of the analyzer is well known, it will not be explained in further detail).

Conventionally, dehumidified gas was guided into the analyzer using a semipermeable membrane vapor phase dehumidifier as explained above with reference to Figure 2, but this semipermeable membrane vapor phase dehumidifier The disadvantage is that the dew point temperature of the gas at the outlet changes depending on the ambient temperature, gas flow rate, pressure difference between the sample gas and the purge drying gas, etc. To solve this problem, the dehumidifier itself is placed in a constant temperature bath and the gas pressure is adjusted. Consideration must be taken to maintain the temperature at a constant level, which has the disadvantage of increasing costs.

This invention was made in order to eliminate the drawbacks of the prior art as described above, and therefore, the purpose of this invention is to adjust the dew point temperature of each gas at the outlet of both dehumidifiers without using an expensive thermostat. It is an object of the present invention to provide a gas analyzer in which the water content of each gas is made the same, thereby making the water content in each gas the same, and in which measurement errors due to water content do not occur.

The main point of the configuration of this invention is that in the conventional gas analyzer as described above, the sample gas discharged from the outlet of one of the two semipermeable membrane vapor phase dehumidifiers is used to dry the sample gas for purging the other dehumidifier. The purpose is to equalize the dew point temperature of each gas at the outlet of both dehumidifiers by using each gas as a gas.

Next, an embodiment of this invention will be described with reference to the drawings.

FIG. 3 is a schematic configuration diagram showing an embodiment of this invention.

Comparing this figure with the configuration of the conventional infrared gas analyzer shown in FIG. 2, the reference gas leaving the dehumidifier 11 is
After passing through the sample cell 14A, the sample gas is used as a purge dry gas for the other dehumidifier 11a, and after passing through the sample cell 14B, the sample gas leaving the dehumidifier 11a is supplied as a purge dry gas to the other dehumidifier 11. You can understand that.

Other than that, there is almost no change.

Note that 17 is a pressure gauge for monitoring the pressure of the reference gas at the outlet of the dehumidifier 11.

In the needle valve material flow meter 12, when the gas flow rate is adjusted to a predetermined flow rate by adjusting the opening degree of the needle valve, the gas pressure changes and the dew point of the gas at the outlet of the dehumidifier 11 may change. Therefore, it is necessary to provide a total of 17 units to monitor the gas pressure.

It goes without saying that the pressure gauge 17a provided on the outlet side of the dehumidifier 11a has a similar function.

Now, in a semipermeable membrane vapor phase dehumidifier, the dew point temperature of the gas at the outlet changes depending on the dew point temperature of the purge drying gas.

There is also some variation depending on the product.

According to the embodiment of this invention, when the dehumidifying capacity of the dehumidifier on the reference side is high (the dew point of the outlet gas is low), the reference gas is used as the drying gas for purging the dehumidifier on the sample side. Gas dehumidifiers increase (dew point decreases).

Since the gas with a high dew point on the sample side is used as a purge dry gas for the reference side dehumidifier, which has a high dehumidifying capacity, the dew point temperature of the reference gas increases, and the dew point temperatures of both gases approach the same value.

FIG. 3A shows the constituent countries of a modified main part of the embodiment shown in FIG.

This figure shows that the pressure gauge 17 can be omitted by using the capillary fixed throttle mechanism 18 in FIG. 3.

A capillary fixed throttle mechanism is composed of a capillary made of an organic compound such as Teflon or polyethylene, and if the flow rate through it is, for example, 0.51/min, the pressure drop there will be 0.5ko/cft. As such, the inner diameter and length of the capillary are appropriately selected so that the relationship between flow rate and pressure drop is fixed, and is known per se.

As shown in FIG. 3A, such a capillary fixed throttle mechanism 18 is provided on the outlet side of the dehumidifier 11, and the opening degree of the bypass needle valve 19 is adjusted so that a predetermined flow rate of gas flows through the mechanism 18.

If a predetermined flow rate of gas flows through the fixed throttle mechanism 18, the pressure drop in the mechanism is fixed, and the outlet pressure of the dehumidifier 11 should also be fixed at a constant value, so the outlet pressure should be monitored. The pressure gauge 17 for this purpose may be omitted.

The same thing can be said about the fixed throttle mechanism 18a and the needle valve 19a.

As explained above, according to this invention, in a conventional gas analyzer, there is no need for an expensive thermostatic chamber, and by simply changing the connection of the gas flow path piping, the reference gas and sample gas can be separated. This method has the advantage of equalizing the water content and making it possible to measure concentration with less error.

In the description of the embodiment, the case where one differential type analyzer is used is illustrated, but it goes without saying that this invention can also be implemented when two non-differential type analyzers are used.

Furthermore, in the embodiment of FIG. 3, the probes 8, 8
We have described an example in which the reference gas and sample gas are sampled independently using the probe 16.16a.
A converter for removing the analytical component gas whose concentration is to be measured may be provided in the reference gas flow path 16, and the outlet gas of this converter may be introduced as the reference gas to the reference cell 14A.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a semipermeable membrane vapor phase dehumidifier, and Figure 1A is a cross-sectional view of a semipermeable membrane vapor phase dehumidifier.
In the figure, a cross-sectional view taken along the line FIG. 3A, which is a schematic configuration diagram showing an example, is a configuration diagram showing a modified main part of the embodiment shown in FIG. In the figure, 1 is an outer tube, 2 is a partition plate, 3 is an inner tube, 4 is an inlet, 5 is an outlet, 6 is an inlet, 7 is an outlet, 8 is a gas sampling probe, 9 is a filter, 10 is a pump, 11 is a Semi-permeable membrane gas phase dehumidifier, 12 a needle valve material flow meter, 13 a filter, 14 an infrared analyzer, 15 a drain pot,
16 is a gas flow path, 17 is a pressure gauge, 18 is a fixed throttle mechanism,
19 indicates a needle valve.

Claims (1)

[Scope of utility model registration request] The first and second semipermeable membrane gases are capable of passing water vapor in the wet gas through the membrane and purging it to the outside by flowing wet gas inside the semipermeable membrane and flowing dry gas for purging to the outside. a phase dehumidifier; a sample cell through which the sample gas dehumidified by the first dehumidifier flows and receives light irradiation;
A reference cell through which the reference gas dehumidified by the second dehumidifier flows and is irradiated with light is provided with means for measuring a difference in transmitted light between the two cells, and a sample is determined from the difference in transmitted light. In a gas analyzer for determining the concentration of gas components in a gas, the sample gas dehumidified by the first dehumidifier is supplied to the second dehumidifier as a purge dry gas, and the sample gas dehumidified by the second dehumidifier is used as a purge dry gas. A gas analyzer characterized in that a reference gas is passed to the first dehumidifier as a purge dry gas.