JPS6216377B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring moisture concentration in a sample gas.

Conventionally, there were no automated instruments for measuring the moisture concentration in sample gases such as exhaust gas, which required time and effort. Furthermore, continuous measurement is not possible, so it is not practical.

Therefore, in view of the above-mentioned drawbacks, the present invention aims to improve this and provide a measuring device capable of continuous automatic measurement.

This invention focuses on the large dielectric constant of water,
The water content is measured by passing a sample gas between parallel electrodes and measuring the capacitance between the electrodes. By the way, the dielectric constant of liquid water has a large value of about 80, but when it is in gaseous form it has a very small value. Therefore, sufficient sensitivity cannot be obtained by filling a sample between the electrode plates forming a capacitor and measuring the water content from the capacitance of the sample. Therefore, an adsorbent with high moisture adsorption capacity is filled between the electrode plates that form the condenser, and the sample gas is passed through this. In this way, adsorption equilibrium is reached depending on the water concentration. At this time, water is retained in the adsorbent in a concentrated form, and the capacitance of the gas sample changes according to the water concentration. Continuous measurement of moisture concentration is possible. By the way, regarding the shape of the electrodes that face each other with this adsorbent sandwiched between them, in order to improve sensitivity, it is preferable to make the adsorbent thinner and to reduce the spacing between the opposing electrode plates. However, if the spacing between the adsorbents is narrowed, it becomes difficult for the sample gas to flow and the response speed decreases. Therefore, in the present invention, as shown in FIG. 1, porous conductive plates 1, 1 are made to face each other with a thin adsorbent 2 interposed therebetween to form a pair of measurement electrodes a. The sample gas 3 is passed through the adsorbent 2 through the porous electrode plates 1, 1. The porous conductive plates 1, 1 are preferably made of a material with excellent corrosion resistance; for example, porous stainless steel is used. Further, the adsorbent 2 is suitably made of a material with good moisture adsorption ability, such as activated alumina. The thickness of this adsorbent 2 may be, for example, about 0.5 mm. In this way, the thickness of the adsorbent is thin and the spacing between the electrodes is narrow, and the sample gas can be supplied directly to the electrodes themselves, resulting in faster measurement response. A specific example of the configuration of the measurement electrode a will be described below.

The measurement electrode a is incorporated into a titanium electrode case b as shown in FIG. 2 in consideration of corrosion resistance. In the figure, reference numeral 4 denotes an electrode case body made of titanium, which includes an intake hole 5 and an exhaust hole 6 for the sample gas.
Then, an exhaust side air chamber 7 is bored, a cylindrical member 8 is welded coaxially with the intake hole 5, and a stud 9 is welded and fixed to the opposite side. Reference numeral 10 denotes an electrode support made of titanium, which has honeycomb-shaped holes 1 for air intake.
1 and an intake side air chamber 12, a screw hole 13 into which an electrode holding frame (described later) is screwed, a through hole 14 into which the cylindrical member 8 is inserted, and a through hole 15 through which the stud 9 is inserted are bored. ing. Reference numeral 16 denotes an electrode case lid made of titanium, which has a guide hole 16' for the sample gas taken in and a through hole 17 into which the stud 9 is inserted. The electrode case body 4, electrode support 10, and electrode case lid 16 are positioned using the cylindrical member 8 and the stud bolt 9, and are tightened and fixed with a nut 9a. Reference numeral 19 denotes electrode holding frames made of titanium, including a first holding frame 19 on the intake side and a second holding frame 2 on the exhaust side.
0, an insulating sleeve 21, and a tightening bolt 22. The measurement electrode a is attached to the first and second holding frames 19, together with the Teflon sealing member 23.
20 and fixed with tightening bolts 22. Reference numeral 24 denotes an electrode extraction body fitted into the electrode case body 4, which includes an electrode extraction part 25 made of Teflon, a contact body holder 27 screwed into a hole 26 in the center of the electrode extraction part, and a contact body holder 2.
The contact body 29 is held in the housing 7 and is pressed against the porous conductive plate 1 by the spring 28, the bolt 30 fixes the electrode extraction part 25 to the electrode case body 4, and the contact body holder 27 is electrically connected to the outside. an external terminal 32 for connecting the electrodes drawn out to the bolts 30 and 31 to an external line;
It is composed of 33.

In this configuration, the sample gas taken in through the suction hole 5 passes through the cylindrical member 8, the guide hole 16', and the honeycomb-shaped hole 11, and enters the suction side air chamber 12. Then, the air passes from the porous conductive plate 1 through the adsorbent 2 to the exhaust side air chamber 7 and is discharged from the exhaust hole 6.
As a result, the adsorbent 2 has a moisture content corresponding to the moisture concentration in the sample gas.

Further, the pair of conductive plates 1, 1 sandwiching the adsorbent 2 are led out to external terminals 32, 33, respectively. That is, one conductive plate 1 is connected to an external terminal 32 via a contact body 29, a contact body holder 27, and a bolt 31.
The other end is connected to the first holding frame 19, the electrode support 10, the stud 9, the electrode case body 4, the bolt 30, and the external terminal 33 in this order. Note that these conductive paths for leading out the electrodes are connected to an insulating sleeve 21 made of Teflon, a sealing member 23 made of Teflon, and an electrode extraction part 25 made of Teflon.
Insulation is maintained by

The electrode b configured in this way is incorporated into the measuring device c shown in FIG. In the same figure, 34
35 is a probe that sucks the sample gas from the flue 34. A heater 36 and a thermostat 37 are incorporated within the probe 35.

The sample gas sucked through the suction hole 39 at the tip of the probe 35 is drawn into the measuring device C via the heating conduit 40. The suction hole 39 is kept warm by an insertion part heater 41 and the heating conduit 40 is kept warm by a heating conduit temperature controller 42 to prevent condensation, and the sample gas is heated to the measuring device C without changing the component ratio. is drawn into the constant temperature bath 43. Inside the constant temperature bath 43, there are a measurement valve 44, a heat exchanger 45, an electrode case b incorporating the measurement electrode a, an evaporator 46 for calibration, a thermostat 47 and a heater 48 in the evaporator 46, and a constant temperature chamber. Temperature controller 49 and its heater 5
0 is placed. The evaporator 46 constitutes a standard gas generation mechanism d for calibration, and can be supplied with an arbitrary amount of water from a pure water tank 51 via an automatic water metering injector 52, and a silica gel cylinder 53 for dehydration. Outside air can be supplied through a dust filter 54. The operation of this evaporator is controlled by opening and closing an evaporator valve 55. next,
On the exhaust side of the thermostatic chamber, 56 is a drain trap, 57 is a drain tank, 58 is an electronic dehumidifier,
59 is a secondary filter, 60 is a sample pump, 61 is a buffer tank, 62 is a flow rate adjustment valve, 63 is a flow meter, and 64 is a sample gas outlet.

This mechanism dehydrates the sample gas after measurement.
The sample pump 60 discharges the sample, and the discharge flow rate is measured by a flow meter 63. The flow rate can be set using the flow rate adjustment valve 62, and this set amount is based on the dry gas. As a result, the sample gas aspirated by the probe 34 is measured on a dry gas basis,
It is convenient to measure because it conforms to the regulatory unit of the Air Pollution Control Act.

In addition, this measuring device also uses the standard gas generation mechanism d.
By operating with the measurement valve 44 closed and the evaporator valve 55 open, the sensitivity can be easily calibrated manually or automatically.

As explained above, this invention measures the capacitance between two opposing conductive plates with a water adsorbent interposed between them, and determines whether water is adsorbed into the adsorbent in accordance with the water concentration in the sample gas. In the water concentration measurement method in a sample gas, which measures the amount of moisture in a sample gas, two opposing porous conductive plates sandwich the film surfaces of a water adsorbent in the form of a thin film, and the sample gas is transferred to the adsorbent. The sample gas passage was partitioned by the conductive plates so that it passed perpendicularly to the membrane surface from one conductive plate to the other. The adsorbent can be passed perpendicularly to the membrane surface, and the membrane surface of the adsorbent can be sandwiched and reinforced with conductive plates from both sides, making it possible to make the adsorbent thinner, making it possible to reduce the adsorption material's influence on the water concentration in the sample gas. The time required to reach a moisture adsorption equilibrium state can be shortened, and sensitivity and response speed can be improved. Further, since the method of the present invention is a physical measurement, no reagent is particularly required, and even if the flow rate fluctuates, the indicated value is not affected.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a measuring electrode to explain the principle of the measuring method of the present invention, Fig. 2 is a side sectional view of an electrode case incorporating the measuring electrode, and Fig. 3 is a block diagram of the entire measuring device. . 1...Porous conductive plate, 2...Adsorbent, 3...
Sample gas, 4... Electrode case body, 5... Intake hole, 6... Exhaust hole, 10... Electrode support, 16...
...Electrode case lid, 18... Electrode holding frame, 24...
... Electrode extraction part, 33, 34 ... External terminal, 34
... Flue, 35 ... Probe, 43 ... Constant temperature chamber,
58...electronic dehumidifier, 60...sample pump, 62
...Flow rate adjustment valve, 63...Flowmeter, a...Measuring electrode, b...Electrode case, C...Measuring device, d
...Standard gas generation mechanism.

Claims (1)

[Claims] 1. A sample gas in which the capacitance between two opposing conductive plates with a water adsorbent interposed therebetween is measured to determine the amount of water adsorbed in the adsorbent according to the water concentration in the sample gas. In the method for measuring the water concentration in water, two facing porous conductive plates sandwich the membrane surfaces of a thin film of water adsorbent, and the sample gas is applied to the adsorbent on one of the conductive plates. A method for measuring moisture concentration in a sample gas, characterized in that a sample gas passage is partitioned by the conductive plate so as to pass perpendicularly to the membrane surface from one conductive plate to the other conductive plate.