JPH0477634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the operation of a device for classifying fine powder, and more particularly to a method for controlling the operation of a device for classifying fine powder entrained in gas.

[Conventional technology]

In response to the demand for the production of micron-level particles and submicron-level particles, the above-mentioned fine particles are obtained by pulverizing the fine powder using a crusher and classifying the pulverized product. is strongly requested.

Conventionally, various devices have been proposed as this type of fine powder classification device, depending on the operating force required for classification. Things are being suggested.

The Coanda effect is a phenomenon in which when a fluid flows along a wall surface at high speed, it adheres to a curved surface such as a cylindrical wall. (For example, "Mechanical Engineering Handbook" Revised 6th Edition (July 20, 1972), P8-15).

As a conventional fine powder classification device that utilizes inertial force and the Coanda effect, an elbow jet classifier and the like have been attempted. (For example, Chemical Engineering Society, "Fine Powder Engineering," (November 1, 1982), Maki Shoten, P158).

Elbow jet classifiers consist of a two-dimensional non-rotating classifier and do not require mechanical methods.
This method uses the Coanda effect to change the direction of airflow, and uses the inertial force of the particles contained in the air as the operating force to perform classification. Air is blown in to carry away the particles, and this Powder floats and moves on the streamlines of the airflow, and coarse powder flows straight forward due to inertial force, so fine powder can be classified into fine powder and coarse powder.

In addition, an airflow containing particles is flowed from the center of the annular classifier with an approximately semicircular cross section along the surface of the classifier to create a fine powder flow containing fine powder and a coarse powder flow containing coarse powder. The inventor has proposed a classification device for fine powder that separates the classification device into two types, and the operation of the classification device is controlled by adjusting the flow rate of gas passing through the classification device, the flow rate of fine powder flow, the flow rate of coarse powder flow, etc. was.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional operation control method for a fine powder classifier, the operation is based on flow rate control of the gas flow rate passing through the classifier, the flow rate of the fine powder flow leading to fine powder, and the flow rate of the coarse powder flow leading to coarse powder. Since this is not controlled, a wall flow that flows along the surface of the classifier will be generated, and the turbulence of this air flow will impede the classification characteristics due to the Coanda effect, causing problems such as the accuracy of fine powder classification. There was a problem that the classification performance deteriorated.

The present invention solves these conventional problems, and provides a simple control system by controlling the ratio of the flow rate of the fine powder flow leading to fine powder from the classifier and the flow rate of the coarse powder flow leading to coarse powder. By using this method, a stable wall flow is formed on the surface of the classifier, and the classification characteristics due to the Coanda effect can be fully utilized, and the classification performance of the fine powder classification device can be significantly improved. The object of the present invention is to provide a method for controlling the operation of a classification device.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention makes a fine powder flow containing fine powder by flowing an air flow containing particles from the center of an annular classifier having an approximately semicircular cross section along the surface of the classifier. In this method, the ratio of the flow rate of the fine powder flow and the flow rate of the coarse powder flow is controlled in a method of controlling the operation of a fine powder classifier that separates the fine powder into a coarse powder flow containing coarse powder.

[Effect]

The present invention has the following effects due to the above configuration. In other words, the flow of the fine powder flow and the coarse powder flow excessively biased to either side is eliminated, and turbulence of the wall flow flowing along the surface of the classifier is suppressed, so the classification characteristics due to the Coanda effect are fully utilized. This makes it possible to significantly improve the classification performance of fine powder.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a classification apparatus for carrying out the method of the present invention.

In Fig. 1, 10 indicates a classifier, and 12
14 represents the inflow area of the airflow containing particles, and 14 represents the classified body, and the surface of the classified body 14 is the inflow area 1.
2, an annular classification surface 16 having an approximately semicircular cross section is formed. Also, O-O is
It shows the central axis of the classifier 10, and the center of the classifier 14 is arranged so as to coincide with the central axis OO. Further, an inductor 18 is movably provided in the center of the classification body 14 so as to coincide with the central axis O-O, and a flow path consisting of an annular region 21 with a narrow gap is formed between the inductor 18 and the inner surface of the classification surface 16. is formed, and the airflow from the inlet region 12 passes through the narrow annular region 21 to become a laminar annular flow 23. The fine powder is supplied from the inflow region 12 as an airflow containing particles together with the airflow, and is sufficiently dispersed to be in a state suitable for classification. , and a flow due to the Coanda effect is formed. Further, the fine powder flow 25 divided by the diverting material 200 of the diverting means 20 is guided to the fine powder discharge port 30 with fine powder floating and accompanying, and
Due to the coarse powder flow 26, the inertial force based on the velocity of the coarse powder corresponding to the speed of the airflow acts as an operating force, and the coarse powder is guided to the coarse powder discharge port 38 in the direction of the central axis O-O, and is discharged. Ru.

FIG. 2 shows a flow sheet of a typical fine powder classification apparatus suitable for operation according to the method of the present invention.

In Fig. 2, numeral 10 indicates a classifier, in which an air stream 11 containing particles for classification is introduced from an inlet region 11, flows along the surface of the classifier, and forms a fine powder stream 25 containing fine particles. Coarse powder flow 2 containing coarse powder
6 and are led to the outside through a fine powder outlet 30 and a coarse powder outlet 38, respectively. fine powder flow 2
5, only the fine powder is collected by the collecting device 250, and then the flow measuring mechanism 252 and the flow rate regulating valve 2
54 and is combined with the coarse powder stream 26. Coarse powder flow 2
6, only coarse particles are collected by a collection device 260, and subsequently passed through a flow rate measuring mechanism 262 and a valve 264, and then merged with the fine powder flow 25. The combined mixed flow 270 is an airflow that does not substantially contain fine particles, and is guided to the outside of the system 278 by a blower 276 via a flow rate measurement mechanism 272 and a flow rate control valve 274.

The fine powder flow 25 is detected by the flow rate measurement mechanisms 252 and 262.
The flow rates of the coarse powder flow 26 and the coarse powder flow 26 are detected, and the ratio of the flow rates of the two is set by the ratio adjuster 286 .The control signal is input to the flow rate adjuster 284 to control the flow rate adjustment valve 254 . Reference numeral 288 indicates a set value, in which the flow rate ratio between the fine powder flow 25 and the coarse powder flow 26 is set in advance.

The flow rate of the mixed flow 270 is detected by the flow rate measurement mechanism 272, and the flow rate adjustment valve 2 is detected by the flow rate regulator 280.
74. Reference numeral 282 indicates a set value, in which the flow rate of the mixed flow 270 is set in advance. mixed flow 270
The flow rate is substantially equal to the flow rate of the airflow 11, which is the flow rate passing through the classifier 10.

Although the flow rate control valve 254 is provided in the 25 fine powder flow lines, it goes without saying that it may also be provided in the 26 coarse powder flow lines. Further, it is also possible to omit either of the flow rate measuring mechanisms 252 and 262, and in this case, the remaining flow rate can be determined by calculation with the flow rate by the flow rate measuring mechanism 272, and the ratio of the flow rate can be controlled. It can be performed.

When controlling the operation of the classifier 10, the flow rate of the mixed flow 270 is controlled so that the air flow 11 corresponding to the processing capacity of the classifier 10 is passed through, and a wall flow is formed on the surface of the classifier. By controlling the operation so as to control the ratio between the powder flow rate and the coarse powder flow rate, the fine powder flow rate and the coarse powder flow rate flow excessively in either direction, resulting in an imbalance between the above flow rates. Stability and turbulence of wall flow can be suppressed. Therefore, it is possible to improve classification performance including classification accuracy in fine powder classification operations.

FIG. 3 shows an explanatory diagram of the ratio control of the fine powder flow rate and the coarse powder flow rate in the classifier of FIG. 1.

FIG. 3a shows the flow state when the fine powder flow 25 and the coarse powder flow 26 flow under an appropriate flow rate ratio.

FIG. 3b shows the flow condition when the fine powder flow 25 flows under an excessive flow rate ratio with respect to the coarse powder flow 26.

FIG. 3c shows the flow condition when the fine powder flow 25 flows under a flow rate ratio that is too small relative to the coarse powder flow 26.

In Figure 3 a, b, c, 16 is the classification surface, 24
indicates a wall flow, 20 indicates a classification means, and 200 indicates a classified material.

In FIG. 3a, a wall flow 24 is formed on the surface of the classification surface 16, a fine powder flow 25 and a coarse powder flow 26.
and flow in equilibrium under an appropriate flow rate ratio, and proper classification of fine powder and coarse powder is performed.

In Fig. 3b, most of the wall flow 24 flows to the fine powder flow 25 side, so even the coarse powder contained in the fine powder is drawn into the fine powder flow 25 side, significantly reducing the classification accuracy. It will end up being put away.

In Fig. 3c, most of the wall flow 24 flows toward the coarse powder flow 26, so even the fine powder contained in the fine powder is drawn into the coarse powder flow 26, significantly reducing the classification accuracy. It turns out.

〔Effect of the invention〕

As is clear from the above embodiments, the present invention eliminates the problem of the fine powder flow and the coarse powder flow being excessively biased toward either one, and also eliminates the turbulence of the wall flow flowing along the surface of the classifier. This has great practical effects, such as making it possible to fully utilize the classification characteristics due to the Coanda effect and significantly improving the classification performance of fine powder.

[Brief explanation of drawings]

Fig. 1 shows a classification device for carrying out the operation control method for a fine powder classification device according to an embodiment of the present invention, Fig. 2 shows a flow sheet for explaining the operation according to the same method, and Fig. 3 shows the flow rate ratio. It is an explanatory diagram of control. 10... Classifying device, 14... Classifying body, 25...
Fine powder flow, 26... Coarse powder flow.

Claims (1)

[Claims] 1 An airflow containing particles is caused to flow from the center of an annular classifier with an approximately semicircular cross section along the surface of the classifier to create a fine powder flow containing fine powder and a coarse powder flow containing coarse powder. 1. A method for controlling the operation of a fine powder classifier which separates fine powder into particles, the method comprising: controlling the ratio of a fine powder flow rate and a coarse powder flow rate.