JPH0713595B2 - Measuring equipment for air pollutants - Google Patents

Description

The present invention relates to an apparatus for measuring an air pollutant, and more particularly to an apparatus for measuring an air pollutant using plasma emission spectrometry.

SUMMARY OF THE INVENTION The present invention is an apparatus for measuring atmospheric pollutants using plasma emission spectrometry, in which a strong electric field is generated by confining an electric field component and a magnetic field component of a high frequency radio wave in a plasma generation unit, and the strong electric field and plasma excitation are generated. By forming a concentrated electric field with the member, plasma can be generated under the conditions of atmospheric pressure and still air.

2. Description of the Related Art There are many different methods for measuring the substances contained in the ambient air, depending on the target substances.

Generally, the procedures are (1) sampling, (2) reaction / extraction such as dissolution / absorption, and (3) analysis.

Regarding the collection of the sample of (1), since a target substance is often present in a very small amount, a method such as long-term absorption is adopted.

Regarding the reaction / extraction such as the dissolution / absorption of (2), a solution such as dissolution with an acid or coloring by a chemical reaction is devised.

The analysis of (3) is also wide-ranging, but the absorptiometry,
Atomic absorption method (FAA), Inductively coupled plasma optical emission spectrometry (IPC)
Law) etc. are known.

Generally, ICP-AES (IPC equipment)
Uses a high-temperature argon gas plasma excitation source, and the excitation source section, the focusing section, the amplification / calculation section, and the data recording section are basic constituent elements.

Furthermore, there are a high-frequency excitation source, a gas supply source, and a sample introduction section, which are attached to the excitation source section.

First, the torch of the excitation source, the cooling part, the auxiliary, and the carrier 3
A kind of argon gas is flowed and high frequency power from an excitation source is applied to the induction coil to generate plasma on the torch.

When the sample solution is introduced into the plasma from the sample introduction part through the nebulizer after the plasma is stabilized, atoms or ions of the element to be measured are excited and emit light. This emitted light is collected and imaged on the entrance slit of the spectroscope, the emission line of the measurement light beam is selected by the spectroscope, and is guided to the detector through the exit slit.

A photomultiplier tube is generally used as the detector. The photocurrent amplified by the photomultiplier tube is amplified by the amplification / arithmetic unit,
The analog quantity is input to the data section as a digital quantity and recorded as a predetermined signal.

Problems to be Solved by the Invention In the IPC method, the frequency (frequency) of microwave used is 2
It is as small as 7.12MHZ or 40.68MHZ, and the oscillator is expensive.

Further, in the IPC method, since argon gas, which is a carrier gas, is introduced into the vacuum container in which the inside of the plasma generation unit is kept at a low pressure, the structure of the plasma generation unit is complicated and the carrier gas introduction unit is It is necessary, and the structure of the entire device is complicated and expensive.

Further, even in the widely used atomic absorption method, preparation of acetylene gas is required to burn acetylene gas, and the apparatus is complicated.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to generate a plasma beam so that the internal pressure in a predetermined hollow container is set to the atmospheric pressure, and further in the hollow container, A large-scale plasma is generated under the condition that there is no gas and only air, and by generating a light beam corresponding to the element to be measured by this, the structure is simple and inexpensive, and high-performance air pollutant It is to enable measurement.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is directed to a plasma excitation unit that oscillates a high frequency radio wave and a circuit that processes the high frequency radio wave generated by the oscillation means. Means, a transmission circuit means for transmitting the high frequency radio wave processed by the circuit means, and a plasma generation means for generating plasma using the high frequency radio wave transmitted by the transmission circuit means. A cavity container for confining an electric field component and a magnetic field component of the transmitted high frequency radio wave, and a cavity resonator formed of a plasma excitation member for forming a concentrated electric field between the electric field component of the high frequency provided in the cavity container. Constitute.

Function In the present invention, when a high-frequency radio wave is transmitted into a cavity resonator composed of a closed hollow container and a plasma excitation member protruding in the hollow container, the electric field component and the magnetic field component of the high-frequency radio wave are It is confined in the cavity resonance and strong electric field and strong magnetic field are induced. A concentrated electric field is formed between the strong electric field and the plasma excitation member, and plasma is generated under atmospheric conditions under atmospheric conditions. When a measurement target is introduced into the plasma, a light beam corresponding to the measurement target element is generated. To do.

This emitted light beam is analyzed by the elemental analysis processing unit to measure the measurement object.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 shows an air pollutant measuring apparatus according to an embodiment of the present invention. Reference numeral 70 denotes a high-frequency power generation processing unit for generating high-frequency power, and reference numeral 50 denotes a high-frequency generation processing unit 70 for generation processing. Transmission circuit for transmitting high frequency power, code 60
Is a plasma generator that generates plasma based on the high-frequency power guided from the transmission circuit 50, and reference numeral 80 is a plasma generator.
A sample supply unit for supplying a sample to 60.

Reference numeral 90 denotes an elemental analysis processing unit, which analyzes the sample based on the light beam generated according to the measurement sample by the plasma generated by the plasma generation unit 60.

The elemental analysis processing unit 90 is a condensing unit 91 that condenses the light beam generated by the plasma generating unit 60, a spectroscope 92 that is a monochromator that receives the light beam condensed by the condensing unit 91 and analyzes the light beam, It is composed of a photomultiplier tube 93, an amplifier 94, and a recorder 95.

The high-frequency power generation processing unit 70 and the plasma generation unit 60 have a configuration schematically shown in FIG.

That is, in FIG. 4, reference numeral 10 is a power supply section, reference numeral 20 is an oscillating section for generating high-frequency radio waves such as microwaves, reference numeral 30 is an operation control section, and reference numeral 40 is a three-dimensional circuit. 10. The oscillating unit 20 and the three-dimensional circuit 40 form a high frequency power generation processing unit 70.

Reference numeral 50 is a transmission circuit section for transmitting high frequency radio waves, and reference numeral 60 is a plasma generation section.

In the power supply unit 10, the number of input phases is 3 and the input voltage is 200V
/ 220V ± 10% (switching method by short bar), input frequency is 50Hz / 60Hz, rectification method is 3-phase full-wave rectification method.

The oscillating unit 20 is a microwave oscillator using a magnetron, and has an oscillating frequency of 2450 ± 30 MHz and an oscillating output of 500 W to 5 kW,
Output stability is 5kW against fluctuation of ± 10% of power supply voltage
Is less than ± 5%, power ripple is less than 10% at an output of 5kW, and the cooling method is water cooling (magnetron) or air cooling (heater of magnetron, antenna).

The operation control unit 30 operates and controls the power supply unit 10 and the three-dimensional circuit 40.

FIG. 5 shows the connection relationship between the oscillation unit 20, the three-dimensional circuit unit 40, the transmission circuit unit 50, and the plasma generation unit 60.
As shown in detail in FIGS. 6 and 7, the taper pipe 41 is connected to the oscillator 20, the isolator 42 is connected to the taper pipe 41, and the directional coupler is connected to the isolator 42.
It is composed of a circuit element composed of 43 and EH tuner 44.

The taper tube 41 connects the oscillator 20 and the isolator 42 without reflection.

The isolator 42 is a waveguide that allows a radio wave to pass in one direction with almost no attenuation, but absorbs a radio wave in the opposite direction and hardly transmits a radio wave, and allows an output radio wave from the oscillation unit 20 to pass therethrough.

Reference numerals 42a, 42b and 42c are cooling pipes. The directional coupler 43 is provided with a coaxial attenuator 45 and a crystal mount 46, respectively, which are used to measure microwaves and which are sub-transmitted depending on the transmission direction of power transmitted on the main transmission line. The transmission direction of the electric power going out to the line is different.
Two coaxial attenuators 45 are provided, one detecting reflected wave power and one detecting traveling wave power.

The EH tuner 44 is equipped with an adjustment knob 47.
By adjusting the insertion / removal of 47, the oscillator 20 is matched with the plasma generator 60 as a load, which will be described later.

The transmission circuit section 50 basically comprises a waveguide as a circuit element and a corner or a bend, and as shown in FIG. 5, a first waveguide 51 and a first waveguide 51 connected to a directional coupler 43. The first E corner 5 connecting the second straight waveguide 52 to the first straight waveguide 51.
6, third straight waveguide 53, second E corner 57 connecting the third straight waveguide 53 to the second straight waveguide 52, and the third straight waveguide 53 connected to the third straight waveguide 53 Fourth straight waveguide 54 and fourth straight waveguide
It is constituted by a fifth straight waveguide 55 connected to 54.

When the shape of the waveguide is determined, the relative distribution of the electric field and the magnetic field in an arbitrary cross section of the waveguide does not change, only the magnitude and phase of the electric field change.

In FIG. 5, the first direct waveguide 51 is connected to the directional coupler 43, the EH tuner 44 is connected to the first direct waveguide 51,
The first corner 56 may be connected to the EH tuner 44.

In addition, the third straight waveguide 53 connected to the second E corner 57
May be removed and the fourth direct waveguide 54 may be directly connected to the corner 57.

A cavity resonance determination 61 is used as the plasma generation unit 60.

As shown in FIG. 2, the cavity resonance determination 61 includes a metallic cylindrical tube 62 which is a hollow container, a metallic lid pair 63 provided at both ends of the cylindrical tube 62, a transparent lid 64 and a plasma excitation member. It is constituted by the metal projection 65.

The cylindrical tube 62 is provided with an opening 66 at the longitudinal center thereof, and the inner wall of the cylindrical tube 62 is provided with a metal piece 65 projecting toward the center of the opening 66.

As an example, a closed surface is made of metal for microwave confinement. At that time, in order to reduce the loss of microwave energy, the shape of the cavity resonator 61 is made cylindrical, its diameter is 161 mm (= 1.318λ, λ: 122 mm at wavelength), and the length of the cylinder is about 3λ. .

Both ends of the cylindrical tube 62 need to be closed, but one end is filled with an almesh plate to make it movable, and the other end is fixed, so it is sealed with aluminum foil.

The reason for using the aluminum mesh plate is to make it possible to observe the inside of the resonator.

The inside of the cavity resonator is set to the same atmospheric pressure as the outside, and only air is used as the gas inside the cavity resonator.

The metal projection 65, which is a plasma excitation member, is one copper wire (diameter 1 mm) and has a length of 120 mm. This is because the induced electric field becomes weak when the length is around 80 mm.

Next, the operation of the air pollutant measuring apparatus according to the embodiment of the present invention will be described.

The power supply unit 10 rectifies AC power and supplies DC power to the oscillation unit 20. The oscillating unit 20 receives the DC power from the power supply unit 10 as an input and performs an oscillating operation to generate high frequency (microwave) power. The output power of the oscillation unit 20 is the three-dimensional circuit unit 40 and the transmission circuit unit.
It is transmitted to the plasma generator 60 through 50.

The operation control unit 30 monitors the current of the power supply unit 10, controls these, and stabilizes the current.
Is trying to stabilize the output radio wave of.

The high frequency radio wave (microwave radio wave) from the oscillator 20 is
As shown in the figure, the taper tube 41 of the three-dimensional circuit section 40 makes it non-reflecting state and is transmitted to the directional coupler 43 through the isolator 42. In the directional coupler 43, the power component of the traveling wave and the power component of the reflected wave are detected.

The operation control unit 30 monitors these power components,
The traveling wave power component in the directional coupler 43 is controlled.

The microwave from the directional coupler 43 is guided to the transmission circuit section 50 through the EH tuner 44. Where EH tuner
Reference numeral 44 seeks to match the microwave power guided from the directional coupler 43 with the load, and makes the microwave power traveling in each straight waveguide of the transmission circuit section 50 into a condition equivalent to non-reflection.

First straight waveguide 51 of transmission circuit section 50, first E corner 5
6, transmitted through the second straight waveguide 52, the second E corner 57, the third straight waveguide 53, the fourth straight waveguide 54, and the fifth straight waveguide 55. The microwave is transmitted to the plasma generator 60.

In the cavity resonator 61 of the plasma generation unit 60, the microwave sent from the fifth straight waveguide 55 forms a standing wave in the cylindrical tube 62 and is confined.

Due to this confinement effect, as shown in FIG. 3, the magnetic field of the magnetic field component H sufficiently cooperating with the magnetic field component Ho of the microwave in the fifth straight waveguide 55 is generated in the axial center line 67 of the cylindrical tube 62. A strong magnetic field E is induced in a donut shape around the axis 67 while being formed substantially symmetrically in a loop shape.

In this case, the electric field E is strong in the magnetic field loop H and becomes almost zero on the axis 57.

Due to this strong electric field E, a strong electric field is further concentrated at the tip of the metal projection 65, which is a plasma excitation member, and the gas (air) in the cylindrical tube 62 is ionized by this electric field concentration, so that the atmospheric pressure is reduced. Plasma is generated in the vicinity of the tip of the metal projecting piece 65 (not in a low pressure or in a vacuum) to generate a fire ball and a light beam corresponding to the elemental component of the sample.

According to the experimental results, it was possible to observe various plasma fireballs in the atmospheric pressure and air in the power range of 1 kW to 2.2 kW.

The first type was a flame located at the end of the waveguide, the color of which changed from orange to blue to red. The size of the flame was 1 to 3 cm and the life was a few minutes.

The second type of plasma fireball was a very bright flash across the entire half-cavity, whitish in color and had a very short life. After a while, the bright flash became a separate fireball, which moved horizontally up and down along the walls of the cavity. Its color was orange and its life was 2-3 seconds.

The third type is plasma generated around the upper portion of the copper wire standing inside the cavity, which is white and has a size of 1 to 5 cm. Some of them came down the copper wire. Life span is 2-3 minutes. A sample is introduced into this third plasma for analysis.

The light beam generated by the plasma generation unit 60 is imaged on the entrance slit of the spectroscope 92 by the condensing unit 91 of the analysis processing unit 90, as shown in FIG. The spectroscope 92 selects the emission line of the measurement light beam and guides it to the photomultiplier tube 93 through the exit slit.

The photomultiplier tube 93 converts the incident light beam into a current signal. The photocurrent photoelectrically converted by the photomultiplier tube 93 is an amplifier 94.
After being amplified by, it is guided to a recorder 95 such as a pen recorder.

The recorder 95 records the response by interlocking with the wavelength scanning of the spectroscope 92 or by manually changing the wavelength of the spectroscope 92 to be discontinuous.

[Advantages of the Invention] According to the present invention, as described above, a high-frequency radio wave is confined in a cavity resonator composed of a closed cavity container and a plasma excitation member provided in the cavity container, thereby achieving a high electric field and a high electric field. After inducing a magnetic field to cause electric field concentration between the high electric field and the plasma excitation member, a large-scale plasma with a simple structure and an inexpensive device in an atmosphere of only air under atmospheric pressure. Since a flame can be generated, a carrier gas or the like is not required, and a simple structure and an inexpensive measuring device for air pollutants can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an air pollutant measuring apparatus according to an embodiment of the present invention, FIG. 2 is a front sectional view of a cavity resonator in a plasma generating portion, and FIG. 3 is a side sectional view of the cavity resonator of FIG. FIG. 4 is a block diagram showing a schematic configuration of a plasma generator according to an embodiment of the present invention, FIG. 5 is a front view of the plasma generator, and FIG. 6 is a front view of the plasma generator without a three-dimensional circuit, Similarly, FIG. 7 is a side view of the three-dimensional circuit unit. 10 ... Power supply part, 20 ... Oscillation part, 40 ... Solid circuit part, 50 ...
… Transmission circuit part, 60 …… plasma generation part, 61 …… cavity resonator, 62 …… cylindrical tube, 63 ・ 64 …… cover, 65 …… plasma excitation member metal projection, 70 …… high frequency power Generation processing unit,
80 ... Sample supply section, 90 ... Elemental analysis processing section

Claims (3)

[Claims] 1. A plasma excitation source excites plasma, introduces an object to be measured into the plasma, generates a light beam corresponding to the object to be measured, guides the emitted light beam to an elemental analysis processing unit, and performs the measurement. In an air pollutant measuring device for analyzing an elemental component of a target substance, the plasma excitation source,
Oscillation means for generating high frequency radio waves, circuit means for processing the high frequency radio waves generated by the oscillation means, transmission circuit means for transmitting the high frequency radio waves processed by this circuit means, and high frequency waves transmitted by this transmission circuit means The plasma generating means is for generating plasma using radio waves, and the plasma generating means has a cavity container for confining the electrolytic component and the magnetic field component of the transmitted high frequency radio wave, and the high frequency wave provided in the cavity container. An air pollutant measuring device comprising a cavity resonator composed of a plasma excitation member for forming a concentrated electric field between the electric field component and the electric field component. 2. A cavity according to claim 1, wherein the cavity resonator is constituted by a cylindrical container made of a metallic cylindrical tube and a metallic lid for closing both ends of the cylindrical tube. Measuring device for air pollutants. 3. The cylindrical container comprises a metallic cylindrical tube, a metallic lid fixed to one end of the cylindrical tube, and a metal tube fixed or movable to the other end of the cylindrical tube. The air pollutant measuring device according to claim 2, wherein the measuring device is constituted by a provided mesh lid.