JPH0342057A - Method and device for classifying fine particle - Google Patents

Abstract

PURPOSE:To precisely classify even fine particles not larger than about 0.1mum by irradiating the photoelectron discharging material with ultraviolet rays and/or radiant ray and imparting electric charge to the fine particles by the generated photoelectrons and classifying them. CONSTITUTION:Photoelectrons are generated by irradiating the photoelectron discharging material 5 with ultraviolet rays emitted from an irradiation source 4 and/or radiant ray. Electric charge is imparted to the fine particles introduced through a gas introducing port 1 by the photoelectrons. The fine particles are classified in a charged fine particle classifying part B1. The fine particles regulated to the constant particle diameter are obtained through a gas conducting port 7. In this case, the unnecessary fine particles are removed by a collection electromagnet 8. Then the comparatively large unnecessary fine particles are removed by the fine holes 9 wherein gas is sucked at constant flow velocity. As a result, even the fine particles not larger than about 0.1mum are precisely classified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for classifying fine particles, and more particularly to a method and apparatus for classifying fine particles charged by photoelectrons.

Fields in which fine particles are classified and used include (1) generators of monodisperse fine particles, (2) equipment for separation and purification of raw materials in the production of new materials, and (3) electronic industry, pharmaceutical industry, food industry, agriculture and forestry. There are devices for separating, classifying, or purifying (high separation) particulate matter in industry, medicine, precision machinery industry, etc.

[Conventional technology]

The conventional classification of fine particles will be described using a dry classification apparatus for fine particles of several micrometers or less, which is a typical classification apparatus. Classification of the fine particles is mainly performed using a centrifugal separator or an inertial classifier.

Classification by these devices all rely on physical effects such as centrifugal force and inertial force, and therefore have the following drawbacks.

(1) The particle size that can be classified is large, and fine particles such as <
Classification of ultrafine particles of 0.1 μm is difficult. Usually 0
．． Only fine particles of 2 to 0.5 μm or more are targeted.

(cutting) Poor classification accuracy, uniform particles (monodisperse particles)
is difficult to obtain.

[Problem to be solved by the invention]

As mentioned above, the conventional techniques have problems in that they cannot classify ultrafine particles and in terms of classification accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method and apparatus for classifying fine particles that can accurately classify fine particles of 0.1 μm or less.

[Means to solve the problem]

In order to achieve the above object, in the present invention, as a classification method, fine particles are classified by being charged with photoelectrons generated by irradiating a photoelectron emitting material with ultraviolet rays and/or radiation, In addition, the classification device has a gas inlet and a gas outlet, and in the gas flow path from the gas inlet to the gas outlet, at least the photoelectron emitting material is irradiated with ultraviolet rays and/or radiation to charge the fine particles. A charging section and a charged particle classification section for classifying charged particles are provided on the downstream side of the particle charging section.

Next, the present invention will be explained in detail.

The material of the photoelectron emitting surface 5 may be any material as long as it emits photoelectrons when irradiated with ultraviolet rays, and a material with a smaller photoelectric work function is preferable. From the viewpoint of effectiveness and economy, Ba,
sr, Ca, Y, Gd, La.

Ce, Nd, Th, Pr, Be,
Zr, Fe, Ni, Zn, Cu,
Eight grams.

Pt, Cd, Pb, Al, C, Mg, Au,
In, Bi, Nb, Si.

Ti, 7a, 31. P or a compound or alloy thereof is preferred, and these may be used alone or in combination of two or more. As the composite material, a physical composite material such as amalgam can also be used.

Compounds include oxides, ferrides, and carbides, and oxides include Ran, Sr, Cab, Y2O3, and Gd.
20t.

NdzOa, Th02. ZrL, PezO
a, ZnO, Cub, ＾g20゜Pt(1,P
b(1,81203.MgO,In2[1a,
There are Ba, NbO, Be[l, etc., and borides include YL and GdBG.

Examples include LaBa, Pryg, 2rB, and carbides such as ZrC, TaC, TiC, and NbC.

In addition, alloys include brass, bronze, phosphor bronze, 8g and Mg.
(Mg 2-20111t%), Cu and Be
(Be is 1 to 10 wt%) and an alloy of 8a and AI can be used.
An alloy of u and Be and an alloy of Ba and AI are preferred.

Oxides can also be obtained by heating only the metal surface in air or by oxidizing it with chemicals.

Still another method is to heat the material before use to form an oxidized layer on the surface to obtain a stable oxidized layer over a long period of time. As an example of this, an oxide thin film can be formed on the surface of an alloy of Mg and 8g in water vapor at a temperature of 300 to 400°C, and this oxide thin film is stable for a long period of time.

These materials can be used in various shapes, such as plate, pleat, lattice, and net shapes, and can be used with their surfaces appropriately roughened. Further, it is possible to use the material in an appropriate shape by applying plating or attaching other materials. As an example of this, Cu-
It is possible to use a Zn material by fixing U-plating or particulate 80.

Further, a photoelectron emitting material having a multilayer structure as already proposed by the present inventor can also be suitably used.

Next, regarding the irradiation of ultraviolet rays and/or radiation, the light source for ultraviolet rays may be any material that emits photoelectrons when irradiated with ultraviolet rays, such as a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, etc. can be used as appropriate.

Similarly, when using radiation, the radiation source may be one that emits photoelectrons upon irradiation, and α-rays, β-rays, T-rays, etc. are used, and cobalt-60, cesium-13, etc. are used as the irradiation means.
7. Radioactive isotopes such as strontium-90, radioactive waste generated in nuclear reactors, and radioactive substances processed appropriately can be used as appropriate.

The use of these materials, ultraviolet light or types of radiation,
It can be determined appropriately depending on the shape of the measuring instrument, field of application, accuracy, economic efficiency, etc.

Furthermore, when the photoelectron emitting material is irradiated with ultraviolet rays and/or radiation in an electric field, photoelectron generation from the photoelectron emitting material occurs effectively.

The method for forming the electric field can be selected as appropriate depending on the shape and structure of the device, the expected effect (accuracy), etc.

The strength of the electric field can be appropriately determined depending on the coexisting moisture concentration, the type of photoelectron emitting material, etc. Dry air (airflow) can be used to classify fine particles, and in this case, the strength of the electric field may be weak.

The voltage of the electric field is 0.01 to 15 kV, preferably 0,0
The voltage ranges from 1 to 5 kV, and the voltage varies depending on the above-mentioned water concentration, the type of photoelectron emitting material, the shape of the device, the material and structure of the electrodes or metals used, and the desired effect.

The strength of the electric field in charging microparticles upon irradiation with ultraviolet light and/or radiation is another invention of the present inventors.

The electrode material and its structure may be those used in ordinary charging devices; for example, a tungsten wire or rod is used as the electrode material.

Charged particles can be classified by appropriately installing electrodes or electric fields. The voltage ranges from 1V to 15kV and can be appropriately determined depending on the shape and structure of the device, the material and structure of the electrodes or metals used, and the effects.

In addition, what particle size fine particles are collected by what kind of electrode (electric field), what kind of pores are used to remove them, or where they are captured or collected are determined by It varies depending on the shape, structure, and conditions of the device, such as the gas flow rate, the strength of the electric field, the degree of the electric field gradient, and the direction of the air flow, that is, whether it is an upward flow, a downward flow, a horizontal flow, or a diagonal direction. This can be determined by conducting a preliminary test or the like using particles of known particle size, or by observing the captured particles using a microscope.

〔Example〕

Examples of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view of the classification device of the present invention. 1st
The figure shows a classification device that uses ultraviolet light.

In FIG. 1, A1 is a particulate charging unit that charges the particulates in the airflow introduced from the gas inlet 1, and B is
A charged fine particle classification section that classifies the charged fine particles is shown.

The fine particles are stirred and mixed in advance in a mixer/regulator 2. Fine particles are entrained in the introduced air by introducing air 3 into the mixer/regulator 2, and large particles of 1 μm or more are removed in advance by an impactor (not shown) or the like, and then introduced into the particle charging section A1. .

The fine particles contained in the introduced air are charged in the charging section A1 by photoelectrons emitted from the photoelectron emitting surface 5 that has been irradiated with ultraviolet rays from the ultraviolet irradiation source 4. Here, the fine particles are efficiently charged, and by selecting appropriate charging conditions, the fine particles are mainly given a monovalent charge.

The particulate charging section A is mainly composed of an ultraviolet radiation source 4, a photoelectron emitting material 5, and an electrode 6.

In this example, an electric field is formed between the photoelectron emitting material 5 and the electrode 6.

The charged fine particles are classified in the charged fine particle classification section B1, and the fine particles having a constant particle size are sent to the gas outlet. More can be obtained.

In the classification section B, the particles are efficiently charged mainly monovalently in the particle charging section A+, so that by appropriately providing electrodes, electric fields, etc., particles of uniform particle size can be effectively obtained.

The charged particle classification section B of this example consists of a collection electrode 8 that mainly captures and removes unnecessary fine particles, and a pore (where a weak electric field is applied and a constant Unnecessary particulates are removed by suctioning gas at a flow rate) 9. Consists of an outlet IO for taking out particulates with a constant particle size.

From the particulate group having a wide particle size distribution charged in the particulate charging section A, unnecessary fine particulates are first removed by a collection electrode 8, and then unnecessary relatively large particulates are gas-sucked at a constant flow rate. Fine particles removed through the pores 9 and having a uniform particle size gather at the outlet lO and are taken out from the gas exhaust lower.

In the example shown in Figure 1, the airflow direction is from top to bottom, but depending on the shape, structure, and intended use of the device, the airflow may flow from bottom to top, or in a lateral or diagonal direction. It is also possible to do this.

In the classification of charged particles in this example, unnecessary fine particles are removed with an electrode, unnecessary relatively large particles are removed with pores, and the remaining particles are obtained at the outlet. The target fine particles (fine particles with uniform particle size) can be taken out by any suitable method without being limited to the above.

For example, by installing multiple sample (fine particle) outlets with an electric field in the sample gas flow path, and by matching the electric field strength and the position of the sample (fine particle) outlets, the desired particle size can be obtained. be able to.

In this example, the particles are charged using an electric field, but it can also be carried out without an electric field.

〔Effect of the invention〕

According to the present invention, the following effects are achieved.

1. By charging microparticles with photoelectrons obtained by irradiating a photoelectron emitting material with ultraviolet rays and/or radiation, ■ Efficiently charging microparticles with a desired particle size to a monovalent charge under appropriate conditions. I can do it.

■ Charged fine particles in ■ can be classified with high accuracy (uniform particle size) by appropriately installing collection electrodes, electric fields, etc.

Ultrafine particles with a particle size of about 2.0.01 to 0.1 μm or less can be easily charged, so they can be classified with high accuracy.

3. The device of the present invention has a simple structure and is easy to operate and maintain, so it can provide an economical and practical classification device.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the classification device of the present invention. A1...Particle charging unit, B1...Charged particle classification unit l...Gas inlet, 2...Mixer/regulator, 3...
Air, 4... Ultraviolet irradiation source, 5... Photoelectron emission surface,
6...electrode,...gas outlet, 8...collecting electrode, 9...pore,...fine particle outlet

Claims (1)

[Claims] 1. A method for classifying fine particles, which comprises classifying fine particles by charging them with photoelectrons generated by irradiating a photoelectron emitting material with ultraviolet rays and/or radiation. 2. The classification method according to claim 1, wherein the photoelectron emitting material is irradiated with ultraviolet rays and/or radiation in an electric field. 3. The classification method according to claim 1 or 2, wherein the photoelectron emitting material is made of a substance with a small photoelectric work function. 4. The photoelectron emitting material is Ba, sr, Ca, Y, Gd
, La, Ce, Nd, Th, Pr, Be, Zr, Fe,
Ni, Zn, Cu, Ag, Pt, Cd, Pb, Al, C
, Mg, Au, In, Bi, Nb, Si, Ta, Ti,
The classification method according to claim 3, wherein the classification method is made of one kind of material selected from Sn, P, and compounds thereof. 5. The photoelectron emitting material is Ba, Sr, Ca, Y, Gd
, La, Ce, Nd, Th, Pr, Be, Zr, Fe,
Ni, Zn, Cu, Ag, Pt, Cd, Pb, Al, C
, Mg, Au, In, Bi, Nb, Si, Ta, Ti,
The classification method according to claim 3, comprising an alloy or composite material of two or more selected from Sn, P, and compounds thereof. 6. The classification method according to claim 3, wherein the photoelectron emitting material is made of one kind of material selected from an alloy consisting of Ag and Mg, Cu and Be, or Ba and Al. 7. The classification method according to claim 3, wherein the photoelectron emitting material is made of one material selected from brass, bronze, and phosphor bronze. 8. The classification method according to claim 1, wherein the photoelectron emitting material has a net shape. 9. The classification method according to claim 2, wherein the voltage of the electric field is 0.01 to 15 kV, preferably 0.01 to 5 kV. 10. The classification method according to claim 1, wherein the charged fine particles are classified using an electric field. 11. The classification method according to claim 10, wherein the voltage of the electric field is 1V to 15kV. 12. A particulate charging unit having a gas inlet and a gas outlet, and in the gas flow path from the gas inlet to the gas outlet, at least irradiating the photoelectron emitting material with ultraviolet rays and/or radiation to charge the particulates. A particulate classification device comprising: a charged particulate classifier for classifying charged particulates on the downstream side of the particulate charging part. 13. The classification device according to claim 12, comprising means for applying an electric field to the particulate charging section and/or the charged particulate classifying part.