JPS60143738A - Manufacture of diluted gas - Google Patents

Abstract

PURPOSE:To make it possible to set a diluting rate, whose dynamic range is wide of selected value, by keeping the pressures of a raw gas and a diluting gas at constant levels, mixing both gases alternately at a specified switching period many times through selector valves, and obtaining a diluted gas having a desired concentration. CONSTITUTION:The pressures of a raw gas 2 and a diluting gas are kept at constant levels by back pressure regulating valves 3 and 3'. A three-way solenoid valve 5 alternately supplies the gas 2 and the gas 1 to a diluted gas path at a preset period. A solenoid valve 17 is opened only when the gas 1 flows and exhausts the gas 2, whose flow rate is controlled by a needle valve 18. Back pressure regulating valves 6 and 6' regulate the pressures of the mixed gas and the gas 1 to the specified values, respectively. The mixed gas is more uniformly mixed in a buffer tank 9. The diluted gas is alternately mixed with the gas 1 at another specified period by a three-way solenoid valve 10 and supplied to a buffer tank 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a method for producing diluent gas. More specifically, it is a method of diluting a high-concentration raw material gas to obtain a gas of a predetermined concentration, and is used to obtain a standard gas for a gas analyzer such as a humidity meter, or to obtain commercially available gases of various concentrations. useful for,
This invention relates to a dilution gas production method.

(b) Conventional technology Conventionally, as a method of diluting gas in multiple stages, the flow of raw material gas is appropriately switched using multiple capillary tubes, etc., and then mixed with a constant flow rate of dilution gas, so-called flow ratio mixing. The law is known.

However, the dilution rate set by this method is fixed, and in order to set a wide range of dilution rates, it is necessary to use many types of capillary tubes, and the accuracy of flow rate control is also affected. There was a limit. Furthermore, when such a method was applied to the production of a standard moisture-containing gas, it was actually difficult to obtain a moisture-containing gas with a low concentration of pp-order because moisture is a component that easily changes its state. .

In addition, oxygen-hydrogen combustion reaction method and permeation tube method are known for producing standard moisture-containing gas, but in the former case, it is difficult to control the reaction rate when producing EIDI-order moisture-containing gas. In addition, there is an element of instability due to changes in the catalyst over time. In the latter case, a water-containing gas on the order of p111 can be obtained, but a water-containing gas on the order of % cannot be obtained, and the dynamic range is narrow. In addition, there is a disadvantage that the method is affected by temperature and the flow rate of diluent gas.

(c) Purpose This invention was made in view of the above-mentioned conventional problems, and it is possible to arbitrarily set a dilution rate with a wide dynamic range from the order of oora to the order of %, and it is possible to adjust the dilution rate such as flow rate coefficient and reaction efficiency. It is an object of the present invention to provide a manufacturing method that does not include a rate correction element and can obtain a diluent gas of a desired concentration with high precision.

(d) Structure Thus, according to the present invention, when producing diluent gas by mixing raw material gas and diluting gas, the raw material gas and diluting gas are maintained at a constant pressure while being controlled at a predetermined value through the switching valve. A diluent gas production method is provided, which is characterized in that the diluent gas is mixed alternately many times at a switching period to obtain a diluent gas having a desired concentration.

The most distinctive feature of this invention is that the mixing ratio of the raw material gas and the diluting gas is determined by the mixing time ratio under a constant pressure. In order to achieve even more uniform mixing, the mixture is alternately repeated many times. Since this method does not set the dilution rate based on changes in physical quantities such as flow (6) and pressure that are likely to change state as in the past, there are fewer variables, and a reliable dilution rate is thereby achieved. I can believe it.

The raw material gas targeted by this invention is not particularly limited. Typical examples include gases such as 02, CO2, NO2, 7 Leon gas, semiconductor gas, and moisture-containing gases. Of course, depending on the equipment, corrosive gases such as CI2 and No. Applicable. On the other hand, the dilution gas used is usually high-purity N2 gas (99,
99%) is preferably used. In addition, when a water-containing gas is used, the raw material gas is prepared by means of saturating water vapor under a constant pressure and temperature, and is dehumidified by passing it through an adsorbent such as P20 Raya molecular sieve as a dilution gas. It is preferable to use high purity N2 gas. Such a combination is particularly useful as a method for producing a standard moisture-containing gas for the calibration of humidity measuring cells.

As described later, the switching valve is a three-way solenoid valve whose switching cycle can be set appropriately. Note that when using the diluent gas continuously, it is preferable to set a buffer tank in the mixing section and use it through this, since the diluent gas can be used more uniformly mixed.

(e) Examples Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a configuration explanatory diagram showing an example of an apparatus used for producing diluent gas according to the present invention. This device basically consists of a diluent gas (1), a back pressure regulating valve (3) and a pressure gauge (4).
A dilution gas supply channel is connected to the three-way solenoid valve (5) through the raw material gas (2), and a raw material gas supply channel is connected to the three-way solenoid valve (5) through the back pressure adjustment stamp and pressure gauge (A). and from the three-way solenoid valve (5) to the back pressure regulating valve (6), the resistance pipe (8) and the pressure gauge (through the buffer tank (9)
) and a diluent gas flow path connected to the In this embodiment, a flow path is connected to a three-way solenoid valve (■) through a back pressure regulating valve (ω) and a pressure gauge (7) in order to further dilute the obtained dilution gas with a dilution gas (1);
A flow path is connected from the buffer tank (9) to the three-way solenoid valve, and the second buffer tank is connected from the three-way solenoid valve to the back pressure regulating valve aυ pressure gauge (+2) and the resistance pipe (13). A flow path connected to (14) is set,
Two stages of dilution can be performed.

The three-way solenoid valves (5) and (g) are each controlled to alternately supply raw material gas and dilution gas to the dilution gas flow path at a predetermined period, and the period can be set arbitrarily using a digital switch, etc. It is configured so that it can be done.

High purity N (99,99%) is used as the diluent gas (1).
), and 1% No gas (f
The operation when using nN2) will be explained.

The raw material gas (2) and dilution gas (1) are each supplied with a back pressure valve (
3), maintained at a constant pressure of 5 koJ at mark. The three-way solenoid valve (5) alternately supplies raw material gas +21 and dilution gas (1) to the dilution gas flow path at a preset period as shown in Figure 3 (in the figure, A indicates the dilution gas flow path). supply cycle, B indicates the supply cycle of the raw material gas). Only when the dilution gas is flowing, the solenoid valve 07) opens and the raw material gas whose flow rate is controlled by the needle is exhausted. The back pressure regulating valves (6) and (0) respectively adjust the pressure of the mixed gas and the diluting gas to 3 kg4.The mixed gas is mixed more uniformly in the buffer tank (9) and becomes a uniform diluting gas. The buffer tank needs to have a sufficiently large capacity compared to the diameter and flow rate of the diluent gas flow path.For example, when using a flow path with an inner diameter of 2.0 m and a flow rate of 500 if/min, the buffer tank must have an inner diameter of at least 100 m.
A buffer tank with a capacity of 1000 CJ is used.

The diluent gas is alternately mixed with the diluent gas at another predetermined period in the same manner as described above and supplied to the buffer tank G4) by the three-way solenoid valve ω). The solenoid valves (15) and (+5) are for misting the respective gases when they do not pass through the three-way solenoid valve and exhausting them through the needles (g) and (6).The back pressure regulating valve aυ is 1. The pressure was regulated to A4 on 5th.

The diluent gas thus diluted in two stages is connected to a desired supply line and used. Of course, in the above apparatus, it is also possible to take out and use gas that has been diluted in one step through the solenoid valve 0. Furthermore, a three-way solenoid valve may be further provided to enable multi-stage dilution.

Table 1 shows the results of attempts to produce NO gas at various dilution rates (1/2 to 1/2000) from 1% NO gas using the apparatus of the above embodiment. In addition, the generated gas flow rate is 300i
f/min, and the operation was performed for 60 minutes per dilution rate of 1, and the measurement of NO1 degrees was performed using a reduced pressure chemiluminescence NO analyzer.

(The following is a margin, continued on the next page) In the table, the time 999, 9: O indicates the case where there is no dilution in the second stage.

As a result, as shown in Figure 4, the intended dilution ratio ^N
The relationship with the diluent gas concentration measured by the O analyzer was almost linear, and good results were obtained for C and V within 5%.

On the other hand, FIG. 2 is a structural diagram showing another example of the apparatus used for producing the diluent gas of the present invention, and particularly shows a standard moisture-containing gas generating apparatus. In the figure, a dehumidifier (lυ) filled with a dehumidifying agent made of molecular sieve 3A is installed in one gas supply channel for dilution, and the raw material gas containing saturated water vapor is The basic configuration is the same as that shown in Figure 1, except that the gas is set to be continuously supplied.When high-purity N2 gas (99,99%) is used as the dilution gas, this gas also contains Since it contains several pp- of water, a dehumidifier (
11) so that its content is 0.19 p- or less.

On the other hand, the raw material gas is a high-purity N2 gas (7) at room temperature that is passed through a humidifier &1) to make it a palm-saturated gas, and then led to a condenser θ whose temperature is controlled at 2°C. A saturated water vapor-containing gas of At this time, the water vapor 11 degrees is i4ooppm. The following operations are the same as above.

Table 2 shows the results of attempts to produce various standard moisture-containing gases by diluting the raw material gas at various dilution rates (1/2 to 1/2000) using the standard moisture-containing gas generator described above.

The flow rate of generated gas was 300/min, the operation was performed for 180 minutes per dilution rate, and the moisture concentration was measured using a humidity measuring cell with a built-in piezoelectric sensor.

(The following margin continues on the next page) As a result, as shown in FIG. 5, the relationship between the intended generated water concentration and the dilution ratio was almost a straight line, indicating that highly accurate dilution was performed.

(f) Effects As stated above, the dilution gas production method of the present invention has the following advantages:
/1101) It has the excellent effect of being able to obtain a wide range of dilution gases from the p order to the % order at any dilution rate and with high precision.

[Brief explanation of drawings]

FIG. 1 is a structural explanatory diagram showing an example of an apparatus used in the dilution gas manufacturing method of the present invention, FIG. 2 is a structural explanatory diagram showing another example of the same, and FIG. 3 is a diagram showing the switching cycle in the manufacturing method of the present invention. Graphs showing time charts, FIGS. 4 and 5, are graphs for explaining the precision of the diluent gas obtained by the manufacturing method of the present invention, respectively. (1)... Dilution gas, (2)... Raw material gas, ■ Back pressure adjustment valve, (4) (7).
...Pressure gauge, (5) ...Three-way solenoid valve.

Claims (1)

[Claims] 1. When producing diluent gas by mixing raw material gas and diluting gas, the raw material gas and diluting gas are maintained at a constant pressure and mixed alternately many times at a predetermined switching cycle via a switching valve. A method for producing a diluent gas, characterized in that a desired diluent gas is obtained.