JPH026352Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a trace water concentration measuring device used for measuring trace water concentration in gases such as propane and methyl chloride.

BACKGROUND ART Conventionally, as a measuring device for measuring trace moisture concentration in gas, a moisture concentration measuring device of a type that measures the heat of adsorption when moisture is adsorbed to a molecular sieve is known.

As shown in Fig. 1, this device divides the sample flow path into two systems 1 and 2, connects a sample introduction pipe 3 and a vent pipe 4 to these flow paths 1 and 2, respectively, and connects one flow path to the other. 1, a dryer 5 for removing moisture in the sample, a flow control valve 6a, a flow meter 7a, and a detector 8a are sequentially installed from the sample introduction tube 3 side toward the vent tube 4 side, and the other flow A flow control valve 6b, a flow meter 7b, and a detector 8b are sequentially installed in channel 2 from the sample introduction tube 3 side toward the vent tube 4 side, and the dryer 5 in one channel 1
Three-way switching valves 9a and 9b are interposed between the flow control valve 6a and the flow control valve 6a of the other flow path 2, respectively, and three-way switching valves 9a and 9b are interposed between the flow control valve 6b of the other flow path 2 and the flow control valve 6b of the other flow path 2. The valve 9b and one flow path 1 are connected to a branch pipe 1, respectively.
Flow control valve 6 at 0a, 10b
It is formed by connecting in front of b and 6a. Here, as the switching valves 9a and 9b, for example, three-way solenoid valves are used. In this case, when the three-way solenoid valve is not energized, C and NO shown in the figure communicate with each other, forming a flow path in the direction of the solid line arrow, whereas when energized, C and NC shown in the figure communicate with each other, and a flow path is formed in the direction of the chain arrow. is beginning to form. Both of the detectors 8a and 8b are filled with a molecular sieve, and a thermistor 1 is inserted into this.
1a and 11b are inserted, and heat generated when moisture in the gas is adsorbed by the molecular sieve is detected by the thermistors 11a and 11b. Note that these thermistors 11a and 11b have the same configuration as the thermal conductivity detector and are a bridge circuit.

In the conventional trace moisture measuring device shown in FIG. 1, the switching valves 9a and 9b are configured to operate simultaneously and repeatedly at predetermined time intervals. For this reason, the detectors 8a and 8b contain the sample gas containing moisture introduced into the flow path 2 and the dry gas obtained by removing moisture from the sample gas introduced into the flow path 1 and containing the same moisture using the dryer 5. (dry sample gas) is alternately and repeatedly introduced at predetermined time intervals. That is,
When the switching valves (three-way solenoid valves) 9a and 9b are not in operation, C and NC communicate with each other as described above, and a flow path is formed in the direction of the solid line arrow, so that the detector 8a
The sample gas introduced into the flow path 1 is connected to the dryer 5.
While the dry gas (dry sample gas) from which moisture has been removed flows through the detector 8b, the sample gas introduced into the flow path 2 flows as it is through the detector 8b. Therefore, in the detector 8b, heat of adsorption is generated by the moisture in the sample gas being adsorbed by the molecular sieve, and the temperature change is detected by the thermistor 11b. Next, switching valves (three-way solenoid valves) 9a, 9b
When operated, C and NC communicate with each other and a flow path is formed in the direction of the chain arrow, so the sample gas introduced into the flow path 2 flows to the detector 8a through the branch pipe 10b, and the flow path The dry gas from which water is removed from the sample gas introduced into the dryer 5 is transferred to the branch pipe 1.
0a to the detector 8b. Therefore, when the switching valves 9a and 9b operate, the sample gas is introduced into the detector 8a and the dry gas is introduced into the detector 8b. Adsorption heat is generated due to the adsorption of
On the other hand, in the detector 8b, moisture adsorbed from the molecular sieve is desorbed by the flow of dry gas, heat is removed, and the molecular sieve is regenerated.

Therefore, since the switching valves 9a and 9b repeatedly perform the above-mentioned operations simultaneously at predetermined time intervals, the output signal of the bridge circuit consisting of thermistors 11a and 11b has a sinusoidal waveform as shown in FIG. The amount of water in the sample gas corresponds to the amplitude H of the waveform.

However, in the conventional trace moisture measuring device of this type as shown in FIG. Therefore, at the start of analysis, be sure to flow dry gas to both detectors 8a and 8b.
It is necessary to stabilize a and 8b, and an additional mechanism is required for this purpose, which has the drawback of complicating the device and increasing the cost of the device. Furthermore, the water concentration corresponds to the distance from the upper limit to the lower limit of one peak, and as shown in Figure 2, the midpoint or zero point of each peak, which is the reference for measurement, is not constant and fluctuates; The apex of the signal may deviate from the chart, making it difficult to read the signal, making it difficult to easily and accurately determine the water concentration, and making signal processing difficult.

The present invention was made to improve the above-mentioned situation, and while dry sample gas is constantly flowing through one detector, dry sample gas and water-containing sample gas to be measured are supplied to the other detector for a predetermined period of time. Therefore, by flowing dry sample gas to both detectors at the start of analysis, the stabilization operation of the detector can be easily performed without any special additional mechanism, and the flow can be switched between both detectors. By comparing the state when dry sample gas is passed through the other detector as the standard, and then the state when water-containing sample gas is flowed through the other detector, the reference state and measurement state are alternately made to appear, and this is repeated. Since measurements can be made while the measurement is being performed, a comparison is always made with the reference state of the measurement system, and from this, the output signal of the bridge circuit is also compared to the balanced state when dry sample gas is flowing to both detectors and the moisture content in the other detector. The peak waveform when flowing the sample gas containing it is repeated, and by measuring the peak height based on the equilibrium state, it is possible to accurately grasp the signal amount corresponding to the water content. It is an object of the present invention to provide a trace water concentration measuring device that is simple, can easily and accurately detect water concentration, and has a simplified method for measuring water concentration.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 3, the same components as those in the trace moisture measuring device shown in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted.

The trace moisture measuring device according to the embodiment shown in FIG. 3 has almost the same configuration as the conventional device shown in FIG. 1, except that the device shown in FIG. interposed, and the detectors 8a, 8
The structure is such that a dry sample is allowed to flow through one of the detectors 8a and 8b, while a water-containing sample gas is allowed to flow through the other. On the other hand, in the embodiment shown in FIG.
This switching valve 9b and one flow path 1 are connected by a branch pipe 10, so that only dry sample gas always flows to one detector 8a, and the other detector 8b By switching the switching valve 9b, the dry sample gas and the moisture-containing sample gas are made to flow alternately at predetermined intervals, and the detector 8a, where the dry sample gas always flows, is used as the reference detector, and the dry sample gas The other detector 8b, through which the water-containing sample gas and the water-containing sample gas flow alternately, is used as a measurement detector. Here, the switching valve 9b can be constituted by, for example, a three-way solenoid valve, and as shown in FIG. 3, when the solenoid valve is not in operation, NO and C communicate with each other, forming a flow path in the direction of the solid arrow. Therefore, the moisture-containing sample gas introduced into the flow path 2 is directly transferred to the other detector 8.
When the solenoid valve is operating, NO and C communicate with each other, forming a flow path in the direction of the chain arrow.
The flow of the moisture-containing sample gas introduced into the flow path 2 is interrupted, and a dry sample gas, which is obtained by removing moisture from the moisture-containing sample gas introduced into the flow path 1 by the dryer 5, flows through the other detector 8b. It is something.

Note that the apparatus shown in FIG. 3 also has each detector 8a, 8
A thermistor 11a is placed in the molecular sieve in b.
11b is inserted, and these thermistors 11a,
11b is assembled into a bridge circuit, and a programmer section 12 is connected to it.The programmer section 12 processes the detection signal sent from the bridge circuit, calculates it as moisture content, and sends the result to the recorder 13. It is now output to . Here, the moisture-containing sample gas and the dry sample gas from which moisture has been removed are alternately passed through the other detector 8b by the operation of the switching valve 9b, and the dry sample gas is constantly passed through the one detector 8a. Therefore, a clear baseline can be obtained for the detection signal, and the signal due to moisture has a peak waveform starting from the baseline, and the programmer section 12 processes the peak area from the baseline.

According to the trace water concentration measuring device shown in FIG. 3, at the start of analysis, if the dry sample gas is made to flow to the other detector 9b by switching the switching valve 9b, both the detectors 9a and 9b are Since the dry sample gases flow simultaneously, both detectors 9a and 9b can be easily and reliably stabilized, and therefore no special additional mechanism is required to dry and stabilize the molecular sieves in both detectors 9a and 9b. This is not the case.

Furthermore, in the device shown in FIG. 3, as described above, thermistors 11a and 11b are inserted into the molecular sheaves in each of the detectors 8a and 8b, and these thermistors 11a and 11b are assembled into a bridge circuit. In this device, dry sample gas from which moisture has been removed always flows through one control detector 8a, and raw sample gas to be measured containing moisture and dry sample gas flow through the other measurement detector 8b. Since the flow is arranged alternately, when the moisture-containing sample gas flows to the other measurement detector 8b, the molecular sieve in this detector 8b adsorbs moisture, causing its temperature to rise, and the switching valve When the dry sample gas flows through the detector 8b by switching 9b, the temperature decreases and returns to the original state. Therefore, the output of the bridge circuit forms a peak waveform, and the magnitude h of this peak corresponds to the amount of water in the water-containing sample gas. It shows clear chromatogram-like peaks as shown in Figure 4, and the signal from the baseline of each peak can be easily read and the signal can be easily processed.

That is, according to the apparatus shown in FIG.
The state when dry sample gas is passed through each detector 8b is used as a reference, and the state where sample gas is then passed through the other detector 8b can be compared. ) can be measured while repeatedly appearing alternately, so that the sample gas flow state (measurement state) is always compared with the reference state.
For this reason, the output signal of the bridge circuit consisting of thermistors 11a and 11b corresponds to the equilibrium state when dry sample gas is flowed through both detectors 8a and 8b, and the equilibrium state when a moisture-containing sample gas is flowed through the other detector 8b. This results in a repetition of the peak waveform at the time, and a peak waveform having a constant baseline as shown in FIG. 4 is obtained. Therefore, by measuring the peak height using the equilibrium state (baseline) as a base line, it is possible to easily and accurately grasp the signal amount corresponding to the water content, and the water content in the sample gas can be measured. That is, in the conventional device shown in Fig. 1, a dry gas (reference side) is alternately supplied to one of the two detectors, and a sample gas containing moisture (measurement side) is supplied to the other, and the moisture content is determined from the output difference between the two detectors. However, in this conventional example, measurement is performed before moisture is sufficiently desorbed from the detector of the reference example, so the baseline fluctuates as shown in Figure 2, and the peak height from the baseline changes. It is not possible to perform signal processing with only this. In other words, in the conventional example, the baseline fluctuates because moisture is adsorbed on the detector (including the flow path leading to it) when the sample gas is passed through it, and when the next time the switch is switched to dry gas, this moisture is absorbed sufficiently. This is because the moisture is not desorbed, and in this case, the greater the amount of moisture adsorbed, the longer it takes for the desorption to occur.In order to sufficiently desorb moisture, it is sufficient to flow dry gas through the detector for a long time, but in the conventional example, if one side is detected If dry gas is allowed to flow through the detector for a long period of time, a sample gas containing moisture will be allowed to flow through the other detector for a long time at the same time, and a large amount of water will be adsorbed to this other detector and the next time the dry gas will flow. Sometimes moisture is not desorbed sufficiently, and as a result both detectors cannot be sufficiently dried.

On the other hand, in this device, one detector 8
Since dry gas is always flowing through a (reference side) and dry gas and moisture-containing sample gas are flowing only through the other detector 8b (measurement side), the output difference between both detectors 8a and 8b is determined. Drying gas can be flowed through this detector 8b until the other detector 8b is sufficiently dried, so that the baseline is stabilized and signal processing can be performed based only on the peak height from the baseline. be.

The apparatus shown in FIG. 3 described above can be suitably used for gases containing trace amounts of moisture, particularly up to about 50 ppm of moisture. Moreover, the molecular sieves 3A and 5A are suitable as the molecular sieves to be filled into the detectors 8a and 8b. Furthermore, the dryer 5 may be any type as long as it can remove moisture from the sample gas.
For example, a freeze dryer or the like may be used, but the most suitable method is one that adsorbs moisture using a molecular sieve. In this case, two dryers filled with molecular sieves can be provided, and one of the dryers can be used for moisture adsorption while the other is regenerated.

Furthermore, when measuring moisture in sample gas,
If the sample gas to be measured containing moisture is continuously introduced into the other detector 8b for too long, the reproducibility of the peak height may deteriorate.
The introduction time is preferably about 20 to 40 seconds,
Furthermore, since a low flow rate causes instability, the sample introduction flow rate is preferably about 2.5 to 3.5/min. Furthermore, in the apparatus having the above configuration, the flow path 1,
2 is preferably kept at a constant temperature from the dryer 5 to the detectors 8a, 8b by using a constant temperature bath or the like.

As described in detail above, the present invention includes a dryer and one detector filled with a molecular sieve inside one flow path connected to the sample introduction tube, and the other flow path connected to the sample introduction tube. A three-way switching valve and the other detector filled with a molecular sieve are interposed in the flow path, and the switching valve and one flow path are connected in front of the one detector via a branch pipe. , a dry sample gas introduced from the sample introduction tube into one flow path and from which moisture has been removed by a dryer is passed through one detector, and a sample gas is supplied to the other detector at predetermined intervals by switching the switching valve. The dry sample gas and the moisture-containing sample gas introduced from the sample introduction tube into the other flow path are alternately flowed, and the moisture in the moisture-containing sample gas is adsorbed by the molecular sieve of the other detector. By measuring the moisture content in the moisture-containing sample gas by measuring the heat of adsorption generated, stabilization of the detector at the start of analysis can be easily performed without any special additional mechanism. In addition to being simplified, the signal output from the detector also shows clear chromatogram-like peaks, and has advantages such as easy signal reading and signal processing.

[Brief explanation of drawings]

Fig. 1 is a flowchart of a conventional trace water concentration measuring device, Fig. 2 is a signal waveform obtained by the same device, Fig. 3 is a flowchart showing an embodiment of the present invention, and Fig. 4 is the same device. This is the signal waveform obtained by . 1, 2...channel, 3...sample introduction tube, 4...
...Bent pipe, 5...Dryer, 8a, 8b...Detector, 9b...Three-way switching valve, 10b...Branch pipe, 11a, 11b...Thermistor.

Claims (1)

[Scope of utility model registration request] One flow path 1 connected to the sample introduction tube 3 is provided with a dryer 5 and a detector 8a filled with a molecular sieve and one detector 8a for detecting temperature changes of the molecular sieve, and connected to the sample introduction tube 3. A three-way switching valve 9b and a detector 8b filled with a molecular sieve and detecting temperature changes in the molecular sieve are interposed in the other flow path 2, and the switching valve 9b and one flow path 1 are connected to each other. are connected in front of one detector 8a via a branch pipe 10, and one detector 8a
A dry sample gas is introduced from the sample introduction pipe 3 into one flow path 1 and water is removed by the dryer 5, and the other detector 8b is supplied with the sample gas at predetermined intervals by switching the switching valve 9b. The dry sample gas and the sample gas containing moisture introduced from the sample introduction tube 3 into the other flow path 2 are alternately flowed, and the output signal of the one detector 8a and the output signal of the other detector 8b are A trace moisture concentration measuring device, characterized in that it is configured to measure moisture in the moisture-containing sample from the difference.