JPH0658891A - Dew point measuring apparatus - Google Patents

Abstract

PURPOSE:To monitor dew point as continuous as possible by thermally evaporating water condensed on a mirror reflection surface through irradiation with microwave or infrared ray or through supply of heated sample gas thereby accelerating cooling-temperature rise cycle. CONSTITUTION:Sample gas is fed through a gas inlet 1, blown against the surface of a mirror 3, and then discharged through a gas outlet 2. Mirror 3 surface is cooled through a cooling head 5 thus condensing water in the sample gas. Consequently, the light from a light source 7 is scattered on the mirror 3 surface and detected at a light receiving section 8. A thermometer 4 indicates dew point temperature and the concentration of water in the gas is calculated. Immediately after measurement of dew point, microwave is projected from a microwave generator 10 through a waveguide 11 to condensed water on the mirror 3 in order to measure dew point again. Water evaporates upon irradiation with microwave. A decision is made that the condensed water has been removed thoroughly if the light receiving section 8 detects no scattering light and the mirror 3 surface is cooled again for the purpose of dew point measurement. Measurement of dew point and removal of condensed water are repeated alternately thus monitoring variation of dew point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dew point measuring device,
In particular, the present invention relates to an optical dew point measuring device for measuring the water concentration in high-purity gas.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional optical dew point measuring device. In the figure, 14 is an outer peripheral container that houses a measurement chamber 16, and a vacuum state is maintained between the outer peripheral container 14 and the measurement chamber 16 by a vacuum exhaust port 9, so that the temperature of the measurement system is affected by the outside temperature. It is a heat insulating space 15 so as not to receive it. Further, 1 is a gas inlet into which a sample gas to be measured is introduced, 2 is a gas outlet from which a gas after measurement is discharged, 3 is a mirror (mirror surface body) arranged in the measurement chamber 16,
Reference numeral 4 is a thermometer for monitoring the temperature of the mirror 3, and 5 is a cooling head of a cooler 17 for cooling the mirror 3. Further, 6 is a heater for removing water condensed on the mirror 3, 7 is a light source for emitting observation light to the mirror 3, and 8 is a light receiving portion for receiving reflected light from the mirror 3.

Next, a method for measuring the dew point will be described. A sample gas to be measured, such as nitrogen or argon, is introduced into the measurement chamber 16 through the gas inlet 1 and is blown onto the mirror 3 while being sequentially exhausted through the gas outlet 2. The mirror 3 is gradually cooled by a cooling head 5 arranged below, and the temperature at this time is measured by a thermometer 4 such as a platinum resistance element.
Is being monitored by. Further, observation light is incident on the mirror 3 from above by the light source 7, and the reflected light is monitored by the light receiving unit 8. Then, when the surface of the mirror 3 is cooled to a temperature equal to or lower than the saturated moisture concentration of the gas to be measured, moisture is condensed on the mirror 3. When this dew condensation is generated, the light irradiated onto the mirror 3 is scattered and detected by the light receiving unit 7.

Then, the temperature at which this scattered light is detected is read by the thermometer 4 and used as the dew point temperature of this gas. The concentration of water contained in the sample gas can be calculated from the obtained dew point. By the way, since the dew point of the sample gas introduced changes with time, in order to measure the dew point again, the dew point of the mirror 3
It is necessary to remove the water on the surface once. Therefore, the temperature of the entire measuring chamber 16 including the mirror 3 is raised by the heater 6 to completely remove the moisture condensed on the surface of the mirror 3. Then, after removing the water on the surface of the mirror 3, the cooling head 5 gradually cools the mirror 3 again, and the dew point (condensation temperature) is measured.

[0005]

Since the conventional dew point measuring device is constructed as described above, in order to monitor the dew point of the gas, which changes with time, it is necessary to remove the dew condensation water. , It is necessary to heat the entire system with a heater, which requires a lot of energy (electric power) and time,
Further, in order to remove the water that has once condensed dew, it is necessary to raise the temperature to a temperature considerably higher than the dew point temperature, and after the temperature rise, the time for cooling to the dew point by remeasurement becomes long,
Therefore, there is a problem that the dew point can be monitored only about once every 30 minutes.

The present invention has been made in order to solve the above-mentioned problems, and evaporates water that has once condensed in a short time while keeping the temperature rise of the system low, and accelerates the cooling-heating cycle. It is an object of the present invention to obtain a dew point side device that can continuously monitor the dew point as much as possible.

[0007]

A dew point measuring device according to the present invention is a sample gas in which moisture condensed on a specular reflection surface is irradiated with microwaves or infrared rays, or heated by a heater provided in a gas introduction pipe. It is provided with a water removing means for heating and evaporating by supplying.

[0008]

In the present invention, since only the water condensed on the specular reflection surface is selectively heated to heat it, dew condensation on the specular reflection surface can be achieved in a short time while keeping the temperature rise of the entire system low. The generated water can be removed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dew point measuring device according to an embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same reference numerals as those in FIG.
4 A microwave generator provided outside, 11 is a waveguide for supplying the output of the microwave generator 10 into the measurement chamber 16.

Next, the operation will be described. Sample gas such as nitrogen and argon is supplied from the gas inlet 1 and blown onto the surface of the mirror 3 in the same manner as in the conventional case, and the sample gas is discharged from the gas outlet 2. At this time, the mirror surface 3 is cooled by the cooling head 5, and the temperature at that time is monitored by the thermometer 4 including a platinum resistance element or the like. Then, when the mirror surface 3 is cooled to a temperature equal to or lower than the saturated water vapor temperature in the sample gas, moisture contained in the sample gas is condensed on the mirror surface 3. Due to this dew condensation, the light emitted from the light source 8 onto the surface of the mirror 3 is scattered and detected by the light receiving portion. The temperature at this time is displayed as the dew point temperature of the sample gas, and the concentration of water contained in the sample gas is calculated from this.

Next, in order to measure the dew point of the sample gas again, which changes with time,
It is necessary to once remove the moisture that has condensed on the mirror surface 3. Therefore, immediately after the dew point is measured, microwaves are radiated from the microwave generator 10 to the condensed water on the mirror surface 3 through the waveguide 11. The irradiated microwaves are selectively absorbed by moisture and converted into heat, and the moisture evaporates, so that the temperature rise of the entire system is smaller than that of the conventional system that heats the entire system. Then, when the scattered light is no longer detected by the light receiving unit 8, it is determined that the condensed water is completely removed, and the surface of the mirror 3 is cooled again for the dew point measurement. Thereafter, the dew point change of the sample gas is continuously monitored by alternately repeating the measurement of the dew point of dew point of the water and the removal of the dewed water by the cooling.

Next, a dew point measuring device according to a second embodiment of the present invention will be described with reference to FIG. In this embodiment, light is used as a method for selectively evaporating the condensed water on the mirror 3. That is, as shown in FIG. 2, reference numeral 12 denotes an infrared irradiator which is arranged so as to focus light on the mirror surface 3 by using a lens or a mirror optical system and remove condensed water. Infrared light should be cut or turned off.

Next, a dew point measuring device according to a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a heated sample gas is used as a method for selectively heating the condensed water on the mirror 3.
That is, as shown in FIG. 3, 13 is a heating coil for heating the gas pipe around the gas inlet 1, and the sample gas heated by the coil 13 has a large amount of saturated steam,
By spraying this on the mirror 3, the condensed water on the mirror can be quickly evaporated and removed. In this case as well, the heating coil 13 is turned off during cooling for dew point measurement.

As described above, according to the first to third embodiments, the dew point can be monitored only once in about 30 minutes, but the cooling-heating cycle is less than half (15). The dew point can be continuously monitored at about double the speed.

Although the heater 6 is not used in each of the above-mentioned embodiments, it may be used as an auxiliary temperature raising means when removing the moisture condensed on the surface of the mirror 3.

[0016]

As described above, according to the dew point measuring device of the present invention, the moisture condensed on the specular reflection surface is selectively applied to the specular reflection surface by applying microwave, infrared rays or heated sample gas to the specular reflection surface. Since this is heated, the dew condensation water can be removed quickly, the temperature rise of the entire system can be suppressed to a low level, and the cooling time for measuring the dew point again can be shortened. Also has the effect of enabling more continuous dew point measurement.

[Brief description of drawings]

FIG. 1 is a sectional view of a dew point measuring device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a dew point measuring device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a dew point measuring device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional dew point measuring device.

[Explanation of symbols]

 1 Gas Inlet 2 Gas Outlet 3 Mirror 4 Thermometer 5 Cooling Head 6 Heater 7 Light Source 8 Light Receiving Section 9 Vacuum Evacuation Port 10 Microwave Generator 11 Waveguide 12 Heating Light Source (Infrared) 13 Heating Coil 14 Outer Container 15 Insulation Space 16 Measurement room

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Ishio 4-1-1 Mizuhara, Itami City, Hyogo Prefecture Mitsubishi Electric Corp.

Claims (2)

[Claims] 1. A specular body and a mechanism for cooling the specular body, sample gas is jetted onto the specular reflection surface of the specular body, and scattering of incident light on the specular reflection surface causes the specular reflection surface to scatter. In the dew point side device for detecting the dew condensation state and measuring the temperature at the time of detection as the dew point of the moisture contained in the sample gas, a gas introduction pipe for injecting the sample gas onto the specular reflection surface of the mirror body, An optical system consisting of a light source that irradiates the specular reflection surface with observation light and a light receiver that receives the reflected light from the specular reflection surface, a temperature sensor that measures the temperature of the specular surface, and water that has condensed on the specular reflection surface. A dew point measuring apparatus comprising: a moisture removing unit that irradiates microwaves or infrared rays to heat and evaporate the dew point. 2. A specular body and a mechanism for cooling the specular body, the sample gas is jetted onto the specular reflection surface of the specular body, and scattering of incident light on the specular reflection surface causes the specular reflection surface to scatter. In the dew point side device for detecting the dew condensation state and measuring the temperature at the time of detection as the dew point of the moisture contained in the sample gas, a gas introduction pipe for injecting the sample gas onto the specular reflection surface of the mirror body, An optical system consisting of a light source that irradiates the specular reflection surface with observation light and a light receiver that receives the reflected light from the specular reflection surface, a temperature sensor that measures the temperature of the specular surface, and water that has condensed on the specular reflection surface. A dew point measuring device, comprising: a water removing unit that supplies and removes the heated sample gas onto the specular reflection surface of the specular body by a heater provided in the gas introduction pipe.