JPH02122875A - Gas circulating type powder classifier - Google Patents

Abstract

PURPOSE:To classify combustible powder by means of a simple structure by circulating non-combustible gas in a circulating line to refluxed gas flow from a discharge pipe of a classifier into a case and classifying the powder. CONSTITUTION:Air in a closed case 6 is sucked in from around a classifier 4 into a pump 11 through a cyclone 7 and a filter 9 and the pump 11 by driving a pump 11, and the air sucked in from a closed case 6 is discharged by opening an air discharge valve 19. When the air in the closed case 6 is almost discharged, the air discharge valve 19 is closed and a nitrogen injection valve 18 is opened to inject nitrogen of given volume, and then the nitrogen injection valve 18 is closed. When a powder to be classified is fed from a feeding inlet 1, the powder is fed into the classifier 4 by a screw feeder 2 and classified. The classifier 4 is operated in the nitrogen atmosphere, and conventional classifier and its piping system can be used as carrier by simply closing the classifier, and classification of combustible powder can be carried out by means of a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas circulation type powder classifier capable of classifying combustible powder.

(Prior art) Air classifiers are used to classify powders with relatively small particle sizes by accelerating the particles using a swirling flow of air and classifying the powder particles by the difference in action between the centrifugal force and the drag force caused by the air flow. It's being used. In this type of air classifier, air is introduced into the classification chamber from the outside, creating a vortex inside the classification chamber, and powder is introduced into this vortex to utilize the balance between centrifugal force and drag caused by the air flow. Classifying powder. Either the airflow flows in from the outside and is exhausted outside the machine through the exhaust pipe in the center of the classifier, or the separated fine powder components are included in this exhaust air, and the coarse powder components move to the outside wall of the classification chamber. Then, the fine powder component and the coarse powder component may be collected respectively.

By the way, when such a classifier is used to classify combustible materials such as fine metal powder, there is a risk that the powder will burn or explode because air is used. Therefore, when using such a classifier to classify flammable powder, install an air seal or rotary feeder around the classifier to shut off the air, and inert gas is introduced into the classifier instead of air. It would be necessary to supply it to a large number of people, or the equipment would become very complex.

(Object and structure of the invention) The present invention has been made in view of the above points, and an object of the present invention is to enable safe classification of flammable powders with a simple structure.

To achieve this objective, a swirling flow is generated in the process of drawing in outside air and discharging it from the exhaust pipe, and powder is introduced into this swirling flow to utilize the difference in action between centrifugal force and drag caused by the gas flow. A classifier for classifying powder using a method, a case for sealing the classifier, and a circulation path for circulating a gas flow from the exhaust pipe of the classifier into the case. It was configured to circulate the powder to classify the powder.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the gas circulation classifier according to the present invention, and in the figure, l represents an inlet into which combustible powder such as fine metal powder is introduced.

Reference numeral 2 denotes a screw feeder that supplies the powder input from the input port 1 to the classifier 4.

The classifier 4 is of a known type, which guides the surrounding outside air into the classification chamber, generates a vortex in the classification chamber, and injects the powder into this vortex, making use of the balance between centrifugal force and drag caused by the gas flow. to classify the powder. The outside air flows in from the circumferential direction of the classifier and is exhausted from the center through the exhaust pipe 4a, or the separated fine powder components are included in this exhaust, and the coarse powder components are discharged to the outside wall of the classification chamber. The coarse powder is moved and collected by the coarse powder conveying pipe 4b. This coarse powder conveying pipe 4b is connected to a coarse powder collection container 5.

The screw feeder 2, the conveying pipe 3, and the classifier 4 are installed in a closed case 6.

A cyclone 7 is connected to an exhaust pipe 4a, and the fine powder components flowing into the exhaust pipe 4a are separated in the cyclone 7 and collected in a fine powder collector 8. 9 is a filter box connected to the cyclone 7 by a pipe lO and used to remove fine powder not collected by the cyclone 7; 11 is a pump connected to the filter box 9 by a pipe 12; and 13 is a temperature -L due to adiabatic compression of gas. A heat exchanger is provided for cooling the pump, and this heat exchanger 13 is connected to the pump 11 by a pipe 14. Furthermore, the heat exchanger 13 is connected to the sealed case 6 through a pipe 15, thus forming a circulation path of the sealed case 6 → cyclone 7 → filter 9 → pump 11 → heat exchanger 13 → closed case 6, and the gas inside is Flows in the direction of the arrow in the figure.

16 is a pressure gauge for measuring the atmospheric pressure inside the sealed case 6; 17 is a relief valve for adjusting the atmospheric pressure inside the sealed case 6;
8 is a nitrogen injection valve connected to the pipe 15, and 19 is an air release valve provided on the pipe 14.

Now, since some air is contained in the sealed case 6 at the time of startup, it is necessary to remove the air and replace the air with nonflammable gas (nitrogen in the embodiment).

Therefore, first, the pump 11 is driven to suck the air inside the sealed case 6 from around the classifier 4 through the cyclone 7 → filter 9 → pump 11, and at this time, the air release valve 19
is opened and the air sucked in from the sealed case 6 is released. On the other hand, the nitrogen cylinder 20 is connected to the nitrogen injection valve 18 in advance, and when most of the air in the sealed case 6 has been removed, the air release valve 19 is closed, the nitrogen injection valve 18 is opened, and a predetermined amount of nitrogen is injected. Thereafter, the nitrogen injection valve 18 is closed. Nitrogen flows into the closed case 6 from the pipe 15, and the classifier a4 operates in a nitrogen atmosphere.

Next, when the powder to be classified is inputted from the inlet 1, the powder is supplied to the classifier 4 by the screw feeder 2, and one classification is started. That is, the nitrogen in the sealed case 6 is sucked in from the outer periphery of the classifier 4 and sent to the cyclone 7 from the exhaust pipe 13, or in the process, the coarse powder is transferred to the coarse powder conveying pipe 4.
The fine powder is collected in a coarse powder collecting container 5 via a cyclone 7, and the fine powder is collected in a fine powder collecting device 8 in a cyclone 7. Nitrogen flows from the cyclone 7 through the filter box 9 to the pump 11. Thereafter, it flows out from the pump 11, is cooled by the heat exchanger 13, and then flows back into the sealed case 6.

With the above method, the conventional classifier and its piping system can be used as is while the classifier is sealed, and combustible powder can be classified with a simple configuration. Furthermore, if the device is operated by opening both the nitrogen injection valve 18 and the air release valve 19, the air classifier becomes similar to the conventional air classifier.

Although the above embodiment deals with the classification of fine metal powder, the present invention is not limited thereto, but is also suitable for classifying other combustible powders such as coal powder and plastic powder. Further, the nonflammable gas is limited to nitrogen, but it goes without saying that an inert gas such as argon or a mixed gas of these and air may be used.

(Effects of the Invention) As described above, according to the present invention, since classification is performed in an atmosphere of nonflammable gas, combustible powder can be safely classified with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the gas circulation classifier according to the present invention. l-...Inlet, 4...Classifier, 6...Sealed case, 7...Cyclone, 9...Filter, 11...
Pump, 18...Nitrogen injection valve, 19...Air release valve, 20...Nitrogen cylinder

Claims (1)

[Claims] A classification method that creates a swirling flow during the process of sucking in outside air and discharging it from the exhaust pipe, inserting powder into this swirling flow, and classifying the powder using the difference in action between centrifugal force and drag caused by the gas flow. the classifier, a case that seals the classifier, and a circulation path that circulates the gas flow from the exhaust pipe into the case, and classifies the powder by circulating nonflammable gas in the circulation path. A gas circulation classifier characterized by: