JPS61120651A - Classification and collection of fine particle - Google Patents

Abstract

PURPOSE:To enable the classification of fine particles with a particle size of up to about several mum - 0.01mum, by changing the intensity of the electric field in a classifier corresponding to the particle size of fine particles to be classified. CONSTITUTION:Solid-gas mixed phase gas containing fine particles and purified sheath air are introduced into a classifier 3 from inlet nozzles 10, 12 and high voltage is applied to a discharge wire 7 and a collection plate 8 to generate corona discharge. Fine particles in the classifier 3 are charged negatively by corona discharge and moved to the plus side of the collection plate 8 and moved vertically by sheath air flowing along the surface of the collection plate 8 in an air curtain form and, therefore, finally moved to the vector direction of the vertical moving speed of sheath air and the horizontal moving speed by corona charge. As a result, when a necessary particle size is classified, by applying a certain constant electric field in the classifier 3, only fine particles to be classified are guided to the collector from an opening part 4.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for classifying and collecting fine particles.

[Problems that conventional technology and inventions attempt to solve] In recent years,
Various new materials, cutting-edge technologies such as geometric element electronics and mechatronics are incorporated into products to improve the added value of products.Products that incorporate this cutting-edge technology use high-purity substances made from new materials. It is important to manufacture powder, but it is also extremely important for functionality to make the particle size of the powder, which is the substance of the intermediate product, uniform.In particular, if coarse particles are mixed into the product, poor performance or quality deterioration will occur. Therefore, it is necessary to make the particles uniform for quality control purposes.

Conventionally, methods for removing and classifying coarse particles in a solid-gas mixed phase fluid have been put to practical use, such as a sedimentation method and a cyclone classification method using centrifugal force.

However, in these classification methods, the target particle diameter is approximately several microns to several hundred microns, and currently no method for classifying fine particles of several microns or less has been put into practical use.

(Objective of the Invention) The present invention was made in view of the above circumstances, and its purpose is to develop a fine particle collection system that can classify and collect fine particles ranging from several microns to approximately 0.1 microns as necessary. The object of the present invention is to provide a classification and collection method.

[Means for solving problems]

In order to achieve the above object, the present invention is characterized by the following method. That is, in the method for classifying and collecting fine particles according to the present invention, a solid-gas mixed phase fluid containing fine particles and a clean sheath gas are introduced into a cylindrical classifier having a slit-shaped opening at a predetermined position in the height direction. A corona discharge is generated in the classifier to charge the fine particles, and the clean sheath gas is caused to flow down like an air curtain along the inner wall of the classifier, and the vertical flow of the sheath gas and the electrostatic force caused by the corona discharge are used to classify the particles. Only the fine particles to be classified are sucked through the slit-shaped opening and guided to the collector, and the fine particles to be classified are collected by the collector.

[Effect]

According to the above method, the particles charged by the corona discharge move in the vector direction of the vertical movement speed of the fluid and the horizontal movement speed by the corona discharge, so a certain electric field is applied inside the classifier. This makes it possible to take out only the fine particles to be classified through the slit-shaped opening.

〔Effect of the invention〕

Therefore, according to the present invention, by changing the electric field strength in the classifier according to the particle size of the fine particles to be classified,
．． It is possible to classify fine particles up to about 1 μm in size, and moreover, these particles can be collected by a collector.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention,
FIG. 1 is a schematic diagram of an apparatus used in this method, and FIG. 2 is a sectional view showing a classifier of the same apparatus. In FIG. 1, 1 is a pipe for introducing a solid-gas mixed phase fluid containing fine particles into the classifier 3, and 2 is a pipe for introducing clean sheath air into the classifier 3. These introduction pipes 1.2 are connected to the upper end of the classifier 3,
The solid-gas mixed phase fluid and clean sheath air are introduced from the upper part of the classifier 3.

The classifier 3 has a cylindrical shape as a whole as shown in FIG. 2, and has a slit-shaped opening 4 at a predetermined position in the height direction.
is provided. A suction pipe 5 for suctioning fine particles to be classified is connected to this opening 4, and the suctioned fine particles are guided to a collector 6 as shown in FIG.

Further, inside the classifier 3, there is a discharge wire 7 for generating corona discharge, and the discharge wire 7 is installed near the outlet of the solid-gas mixed-phase fluid inlet nozzle 10 fixedly installed at the upper end of the classifier 3, and 8 is lined on the inner wall of the classifier 3 with an insulating member or the like interposed therebetween.

Further, a cylindrical rectifying member 11 is arranged concentrically in the upper part of the classifier 3, and allows the clean sheath gas introduced from the sheath gas inlet nozzle 12 to flow down vertically in an air curtain shape along the collection plate 7. It looks like this. Also classifier 3
A discharge pipe 13 for discharging fine particles adhering to the collection plate 8 is connected to the lower opening of the collection plate 8 . In addition, 14 in the figure
is a transformer, 15 is an exhaust gas suction fan, 16a, 16b
, 16C is a gate valve.

Next, the operation of the above embodiment will be explained.

First, a solid-gas multiphase fluid containing fine particles and clean sheath air are introduced into the classifier 3 through the solid-gas multiphase fluid inlet nozzle 10 and the sheath air inlet nozzle 12, respectively, and a high voltage is applied to the discharge wire 7 and the collection plate 8. corona discharge is generated within the classifier 3. Here, the fine particles in the classifier 3 are negatively charged by the corona discharge and move toward the positive side of the collection plate 8, and are also moved vertically by the sheath air flowing in an air curtain shape on the surface of the collection plate 8. Therefore, the fine particles introduced into the classifier 3 move at the vertical movement speed V of the sheath gas.
It moves in the vector direction of y and the horizontal movement speed Vx due to corona discharge.

Here, the vertical movement speed VY and horizontal movement speed Vx are (
It is expressed by formulas 1) and (2).

Vy=D/S... (1) Vx=ZpE... (2> In the above equation, Q: total gas fit (cm3/sea
3: Front gas passage area (α2), Zp: Electrical mobility (aR2/volt 5ec), E: Electrical strength (e
-su), and Zp is expressed by formula (3).

Zp-(,QE”/127r・μg)Dp-(3)
In the above equation, Dp: particle diameter (μ), dielectric coefficient of 92 particles, μg: gas viscosity (C-1)).

From equation (3), Zp is proportional to the particle diameter Op, and (2
) by considering the electric field strength E of the equation.

The fine particle diameter Dp at the Y point can be calculated.

Therefore, when classifying the required particle size, by applying a certain electric field E in the classifier 3, only the fine particles to be classified are sucked through the opening 4, and passed through the suction tube 5 to the collector 7. be guided. In the collector 7, a positively charged collection plate (
(not shown), the negative charge*m particles sucked through the opening 4 are collected on the collection plate.

Incidentally, fine particles whose particle size is smaller than the particles to be classified do not pass through the opening 4 and are collected by the collection plate 8 above the opening 4, and larger coarse particles are collected by the collection plate 8 at the center of the opening 4. be captured.

Furthermore, if a large amount of particles adhere to the collection plate 8 in the classifier 3, the performance will be degraded, so a dusting operation is performed intermittently. The key to the dusting operation is to first stop the supply of the solid-gas mixed phase fluid, fully close the gate valves 16a and 16b to collect as much of the classified fine particles as possible in the collector 6, and then remove the trapped particles in the classifier 3. Particles adhering to the collection plate 8 may be knocked off by hammering or the like, and the gate valve 16c may be opened to guide the particles through the discharge pipe 13 to the collector 6, where the particles may be collected.

As described above, according to this embodiment, fine particles in a solid-gas mixed phase fluid can be classified and collected according to particle size, so that it is possible to prevent coarse particles from being mixed into a product. According to experiments conducted by the present inventors, combustion exhaust gas with a particle size distribution as shown in Table 1 can be classified as a solid-gas multiphase fluid! ! ! Approximately 2J2/ within 3
1n is introduced, and along with this, sheath air is introduced at about 110β/ak.
When the particles were introduced into the classifier 3 and a certain voltage was applied inside the classifier 3, fine particles of approximately 0.1μ could be taken out from the opening 4 as shown in Table 2.

Table 1 Particle size distribution in solid-gas mixed phase sub-product (before classification) Table 2 Particle size distribution obtained from the opening of the classifier

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a schematic diagram of an apparatus used in this method, and FIG. 2 is a sectional view showing a classifier of the same apparatus. DESCRIPTION OF SYMBOLS 1... Solid-gas mixed phase fluid introduction piping, 2... Sheath air introduction piping, 3... Classifier, 5... Suction pipe, 6... Collector.

Claims (1)

[Claims] A solid-gas mixed phase fluid containing fine particles and a clean sheath gas are introduced into a cylindrical classifier having a slit-shaped opening at a predetermined position in the height direction, and a corona discharge is generated within this classifier to remove the fine particles. While being charged, the clean sheath gas is caused to flow down like an air curtain along the inner wall of the classifier, and only the fine particles to be classified are sucked through the slit-shaped opening and captured by the vertical flow of the sheath gas and the electrostatic force generated by the corona discharge. A method for classifying and collecting fine particles, which comprises introducing the fine particles to a collector and collecting the fine particles to be classified in the collector.