JPH0477632B2 - - Google Patents

Description

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

[Prior Art] 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 them with a pulverizer and dispensing a pulverized product of the fine powder. In particular, there is a strong demand for more precise classification.

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, 1982), 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, "Powder and Granule Engineering," (November 1, 1986), 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 The powder floats and moves on the streamlines of the airflow, and the coarse powder flows straight down due to inertia, so the fine powder can be divided 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.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional operation control method of a fine powder classifier, the pressure of the fine powder flow and the pressure of the coarse powder flow in the classifier, including the amount of air and fluid passing through the classifier, is Since the operation control based on pressure control is not performed, turbulence occurs in the wall flow flowing along the surface of the classifier, and this turbulence in the airflow obstructs the classification characteristics due to the Coanda effect, resulting in fine powder There was a problem in that the classification performance, including the classification accuracy, deteriorated.

The present invention solves these conventional problems by using a simple control system by performing pressure control to equalize the pressure of the fine powder flow and the pressure of the coarse powder flow in the classifier. This is an excellent fine powder classifier that can significantly improve the classification performance of the fine powder classifier by forming a stable wall flow on the surface of the classifier and making full use of the classification characteristics due to the Coanda effect. The purpose of this invention is to provide an operation control method.

[Means for Solving the Problems] In order to achieve the above object, the present invention directs an airflow containing particles from the center of an annular classifier having an approximately semicircular cross section along the surface of the classifier. In a method for controlling the operation of a fine powder classifier that flows and separates into a fine powder stream containing fine powder and a coarse powder stream containing coarse powder, in order to equalize the fine powder flow pressure and the coarse powder flow pressure in the classifier. This system is designed to perform pressure control.

[Function] The present invention has the following effects due to the above configuration. In other words, the fine powder flow and the coarse powder flow are prevented from flowing excessively in either direction, 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, an example 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 an inflow region of the airflow containing particles, and 14 represents a classification body. The surface of the classification body 14 continues to the inflow region 12, and an annular classification surface 16 having an approximately semicircular cross section is formed. ing. Also, O-O
indicates 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 is movably provided in the center of the classification body 14 so as to coincide with the central axis O-O, and between it and the inner surface of the classification surface 16,
A flow path consisting of an annular region 21 with a narrow gap is formed, and the airflow from the inlet region 12 flows through the narrow annular region 21.
, and becomes 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.
In a state suitable for classification, the annular flow 23 that has passed through the narrow annular region 21 continues to become a wall flow 24 and flows along the classification surface 16 to form a flow due to the Coanda effect. Furthermore, the flow dividing means 20
The fine powder flow 25 diverted by the diverting material 200 is guided to the fine powder discharge port 30 with fine powder floating and accompanying.
In addition, the inertia force based on the speed of the coarse powder corresponding to the speed of the airflow by the coarse powder flow 26 acts as an operating force and is guided to the coarse powder discharge port 38 in the direction of the central axis O-O, and each of the coarse powder is discharged. be done.

P25 indicates the detection position of the fine powder flow pressure in the classifier, and P26 similarly indicates the detection position of the coarse powder flow pressure.

Although the above-mentioned detection position is provided inside the classifier 10, it may also be provided in the fine powder flow 25 piping and the coarse powder flow 26 piping which are close to the classification device 10.

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 12, 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 from the fine powder outlet 30 and the coarse powder outlet 38, respectively. fine powder flow 2
5, only fine particles are collected by a collection device 250, and then passed through a control valve 254 and merged with coarse particles 26. Only the coarse particles 26 are collected by the collecting device 260 and then passed through the control valve 264.
It is combined with fine powder particles 25. Combined mixture 27
0 is an airflow that does not substantially contain fine powder, 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 pressure of the fine powder flow 25 at the detection position P25 is measured by the pressure measurement mechanism 252, and the pressure of the fine powder flow 25 at the detection position P25 is measured by the pressure measurement mechanism 252.
4, the operation signal controls the control valve 254. Further, the pressure of the coarse powder flow 26 at the detection position P26 is measured by the pressure measurement mechanism 262, and the operation signal is sent to the control valve 264 by the regulator 285.
control. Reference numeral 286 indicates a pressure regulator, and based on the set value 288, a signal is sent to the regulator 28 to equalize the pressure of the fine powder flow 25 and the pressure of the coarse powder flow 26.
4,285.

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.

The flow rate of the mixed flow 270 is substantially equal to the flow rate of the air flow 11, which is the flow rate through the classifier 10.

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 to equalize the pressure of the fine powder flow 25 and the pressure of the coarse powder flow 26 at the detection positions P25 and P26 of the device 10, the fine powder flow 25 and the coarse powder flow 26 can be adjusted. It is possible to prevent the flow from being excessively biased in either direction, destabilizing the equilibrium state, and causing turbulence in the wall flow. That is, with the above operation control method, for example, most of the wall flow 24 flows to the fine powder flow 25 side, and even the coarse powder contained in the fine powder is drawn into the fine powder flow 25 side, reducing the classification accuracy. It will be possible to eliminate the significant decrease in Therefore, it is possible to improve classification performance including classification accuracy in fine powder classification operations.

[Effects of the Invention] As is clear from the above embodiments, the present invention eliminates the fact that the fine powder flow and the coarse powder flow flow excessively toward either side by pressure control, and also prevents the fine powder flow and the coarse powder flow from flowing excessively in either direction. Since the turbulence of the wall flow flowing along the wall surface flow is suppressed, the classification characteristics due to the Coanda effect can be fully utilized, and the practical effects are great, such as the ability to significantly improve the classification performance of fine powder.

[Brief explanation of the drawing]

FIG. 1 shows a classification device for carrying out an operation control method for a fine powder classification device according to an embodiment of the present invention;
FIG. 2 is a flow sheet for explaining the operation according to the method. 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 having an approximately semicircular cross section along the surface of the classifier to form a fine powder flow containing fine powder and a coarse powder flow containing coarse powder. A method for controlling the operation of a fine powder classifier to be separated, the method comprising: performing pressure control to equalize fine powder flow pressure and coarse powder flow pressure in the classifier.