KR101609408B1 - Method for classifying powder - Google Patents

Abstract

In the powder classifying method using a fluid classifier, a mixing step (step (S10)) of mixing a powder composed of nickel and a preparation made of an organic solvent having a flash point of 80 ° C or higher (step (S10)), (Step S22) for injecting the gas into the fluid classifier, a heating step for heating the gas (step S14), a supplying step for supplying the gas heated in the heating step to the fluid classifier (Step S16); and a classifying step (step S24) of classifying the powder on the particle size in the fluid classifier.

Description

[0001] METHOD FOR CLASSIFYING POWDER [0002]

The present invention relates to a method of classifying powders that effectively classify powder having a particle size distribution at a desired classifying point (particle size).

There has been known a classifying method in which a powder such as a glass-made blast furnace slag is classified into a fine powder and a coarse powder by adding a liquid such as an alcohol in advance to the classifying method (for example, see Patent Document 1). In this classification method, a preparation containing a polar molecule is added to the powder to electrically neutralize the polarity of the powder particle, thereby preventing the particles from being adsorbed and aggregated to form aggregated particles having a large particle size, .

Japanese Patent Application Laid-Open No. 1989-85149

However, today, as an internal electrode of the multilayer ceramic capacitor, a very small nickel fine powder having an average particle diameter of 1 mu m or less is used. In order to obtain a high-quality multilayer ceramic capacitor, not only the average particle diameter is extremely small but also the width of the particle size distribution is extremely narrow, that is, a more homogeneous powder is required. However, in the conventional classifying method by centrifugal separation, powder of the raw material adheres to each part in the classifier, and the inlet of the raw material and the outlet of the high-pressure gas are closed, so that the classifying performance is deteriorated and it is difficult to operate for a long time .

The object of the present invention is to provide a method of classifying powder capable of classifying powder with high precision.

The method of classifying powder according to the present invention is a method of classifying powder using a fluid classifier, comprising the steps of mixing a powder made of nickel and an organic solvent having a flash point of 80 ° C or higher; A heating step of heating the gas; a supplying step of supplying the gas heated in the heating step to the fluid classifier; and a step of supplying the powder in the fluid classifier And classifying based on the particle size.

The method of classifying powder according to the present invention is a method of classifying powder using a fluid classifier, comprising a mixing step of mixing a powder made of nickel and a preparation made of water, and a step of putting the powder mixed in the mixing step into the fluid classifier A heating step of heating the gas; a supplying step of supplying the gas heated in the heating step to the fluid classifier; and a classifying step of classifying the powder on the basis of the particle size in the fluid classifier .

According to the powder classification method of the present invention, it is possible to classify powder with high precision using water or an organic solvent having a high flash point as a preparation.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic configuration diagram showing a configuration of a classification apparatus according to a first embodiment; Fig.
Fig. 2 is a longitudinal sectional view showing the internal configuration of the classifier according to the first embodiment,
3 is a cross-sectional view showing the internal structure of the classifier according to the first embodiment,
4 is a flow chart for explaining a powder classification method according to the first embodiment,
5 is a flow chart for explaining a powder classification method according to the second embodiment;

Hereinafter, a method of classifying a powder according to the first embodiment of the present invention will be described with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic structural view showing a structure of a fluid classifier used by a powder classifying method according to the present embodiment. FIG.

As shown in Fig. 1, the classifier 2 includes a classifier (fluid classifier) 4 for classifying powder charged as a raw material by a swirling air flow generated therein, and a powder feeder A blower 8 for supplying a high pressure gas to the classifier 4 and a first heater 10 for heating the supplied high pressure gas to a predetermined temperature. The classification apparatus 2 further includes a suction blower 12 for sucking and collecting the fine particles separated up to a desired classification point together with the gas in the classifier 4, A second heater 14 for heating the atmosphere (atmospheric pressure gas), and a recovery container 16 for recovering centrifugal coarse particles.

The classifier 4 having a roughly conical shape is provided with the apex of the cone facing downward. A centrifugal chamber 20 (see FIG. 2) described later is formed in the upper part of the classifier 4 have. In the centrifugal separation chamber 20, atmospheric air as an atmospheric gas existing outside the classifier 4 and a high-pressure gas from the blower 8 are supplied, and at the same time, powder as a classification target is fed from the feeder 6 .

The feeder 6 has a screw (not shown) therein, and by rotating the screw, powder contained therein can be quantitatively delivered. The discharged powder is injected into the classifier 4 through the inlet 26 (see Fig. 2) provided on the surface of the classifier 4. [ The powder contained in the feeder 6 is previously mixed with the preparation described below in detail.

The blower 8 compresses the atmosphere to generate a high-pressure gas, and supplies the gas to the classifier 4 via the first heater 10. The first heater 10 has a pipe through which a high-pressure gas passes, and a heating means such as a filament or an aerofin is provided in the pipe. The heating means heats the high-pressure gas passing through the pipe to a predetermined temperature and removes moisture contained in the high-pressure gas. Further, another dehydrating means for removing moisture contained in the high-pressure gas may be separately provided between the blower 8 and the classifier 4, or a filter for removing dust or the like may be suitably provided.

The suction blower 12 is configured to separate the fine particles separated by the classifier 4 from the suction port 32 (see FIG. 2) provided at the center of the upper surface of the classifier 4 together with the gas existing in the classifier 4 Recover by inhalation. Further, a filter such as a bug filter may be suitably provided between the suction port 32 and the suction blower 12. Here, when the suction blower 12 sucks the gas, a negative pressure is generated in the classifier 4, so that atmospheric air existing in the outside of the classifier 4 is sucked into the classifier 4. As the atmospheric gas is sucked in this way, a swirling airflow rotating at high speed is formed in the centrifugal chamber 20 of the classifier 4. [ Since the classifier 2 according to the present embodiment is provided with the second heater 14 that heats the atmospheric pressure gas to be sucked, the temperature of the swirling airflow in the centrifuge chamber 20 is heated to a predetermined temperature . Like the first heater 10, the second heater 14 has therein a pipe through which an atmospheric gas passes, and a heating means such as a filament or an aerofine is provided in the pipe.

The recovery vessel 16 is provided at the lowermost part of the classifier 4 and recovers the debris falling along the inclined plane of the conical section of the classifier 4 after being centrifuged in the centrifuge chamber 20.

Next, the classifier 4 according to the present embodiment will be described with reference to Figs. 2 and 3. Fig. FIG. 2 is a longitudinal sectional view of the classifier including the central axis of the classifier 4, and FIG. 3 is a transverse sectional view at the position of the centrifugal chamber 20 by a plane perpendicular to the central axis. In order to clarify the relative positional relationship with other components (in particular, the ejection nozzle 30 and the guide vane 40 described later), the inlet port 26 and the ejection nozzle (30) are shown by imaginary lines and dotted lines, respectively. Further, only two ejection nozzles 30 are shown for explanation.

2, an upper disc-like member 22 having a flat disc shape and a lower disc-shaped member 24 having a hollow disc-shaped inner portion are arranged at a predetermined interval in the upper portion of the classifier 4 And a cylindrical centrifugal chamber 20 is formed between both disk-shaped members. An inlet 26 through which the powder injected from the above-described feeder 6 passes is formed above the centrifugal separation chamber 20. 3, a plurality of guide vanes 40 are arranged at equal intervals on the outer periphery of the centrifugal separation chamber 20, and on the lower side of the centrifugal separation chamber 20, a lower disk- A re-classifying zone 28 for returning the powder dropped from the centrifugal chamber 20 back into the centrifugal chamber 20 is formed.

In the vicinity of the upper end portion of the outer peripheral wall of the re-classifying section 28, the jetting nozzle 30 for jetting the high-pressure gas supplied from the blower 8 described above is arranged so as to be almost the same as the tangential direction of the outer peripheral wall . The spray nozzle 30 sprays a high-pressure gas to disperse the powder injected from the inlet 26, and supplies the gas into the centrifugal chamber 20 in an auxiliary manner. In addition, the fine particles present in the re-classifying zone 28 are returned into the centrifuge chamber 20. In this embodiment, six ejection nozzles 30 are disposed on the outer peripheral wall of the re-classifying zone 28. This is an example, and the position and the number of the ejection nozzles 30 are flexible.

At the center of the upper portion of the centrifugal separation chamber 20, there is provided a suction port 32 for sucking and recovering the coarse powder and the separated fine particles by centrifugal separation. The centrifugally separated coarse powder descends the inclined surface of the conical portion of the classifier 4 from the re-classifying section 28 and is discharged from the discharge port 34 provided at the lowermost part of the classifier 4, 16).

As shown in Fig. 3, a guide vane 40 is disposed at the outer periphery of the centrifugal separation chamber 20 to form a swirling air flow in the centrifugal separation chamber 20 and adjust the swirling velocity of the swirling air flow have. In the present embodiment, as an example, 16 guide vanes 40 are arranged. The guide vane 40 is rotatably supported between the upper disk-shaped member 22 and the lower disk-shaped member 24 by a rotary shaft 40a, and is rotatably supported by the pin 40b The guide vane 40 is fixed to a copper plate (pivoting means), and by rotating the pivot plate, all the guide vanes 40 can be simultaneously rotated at a predetermined angle. By changing the interval between the guide vanes 40 by rotating the guide vane 40 by a predetermined angle in this manner, the flow rate of the atmospheric gas passing through the gap in the direction of the white arrow shown in Fig. 2 is changed, The flow velocity of the swirling airflow in the centrifugal separation chamber 20 can be changed. By changing the flow velocity of the swirling airflow in this way, the classifying performance (specifically, classifying point) of the classifier 4 according to the present embodiment can be changed. As described above, the atmospheric gas passing through the gap between the guide vanes 40 is an atmospheric gas heated to a predetermined temperature by the second heater 14 in advance.

Next, the method of classifying powder according to the present embodiment will be described with reference to the flowchart of Fig. First, mixing of the powders, which is the object of classification, with the liquid is carried out (step S10). Here, the kind of the auxiliary agent to be used may be appropriately selected according to the kind of the powder to be classified. However, when the object to be classified is powder of nickel, as in the powder classifying method according to the present embodiment, an example of water or glycols It is preferable to use an organic solvent having a flash point of at least 80 캜 such as diethyleneglycol (flash point 124 캜). In addition, in the method of classifying a powder according to the present embodiment, it is preferable to add a predetermined amount of preparation to the powder to be classified and then to mix the powder with a mixer Mixing. Further, since the auxiliary agent added to the powder is partially evaporated during mixing with the powder and after mixing, the amount of the auxiliary included in the mixed powder when the mixed powder is put into the feeder 6 of the classifying device 2, The amount of the preparation added to the cigarette is reduced.

Also, Hi-X (manufactured by Nisshin Engineering Co., Ltd.) is used for the mixer.

When the classification apparatus 2 is activated, the suction of the gas is started by the suction blower 12 (step S12). Since the gas in the centrifugal separation chamber 20 is sucked from the suction port 32 provided in the upper center of the centrifugal separation chamber 20, the air pressure at the center of the centrifugal separation chamber 20 is relatively lowered. By the negative pressure generated in the centrifugal separation chamber 20 in this way, air as the atmospheric pressure gas is sucked from among the guide vanes 40 disposed along the outer periphery of the centrifugal separation chamber 20, (Step S16). Further, the atmospheric pressure gas sucked into the centrifugal separation chamber 20 is preheated to a predetermined temperature by passing through the piping provided in the second heater 14 (step S14). As described above, the atmospheric gas is sucked from between the guide vanes 40 to form a swirling flow having a flow velocity determined according to the rotation angle of the guide vane 40. Further, in the powder classification method according to the present embodiment, the atmospheric pressure gas to be sucked is heated so that the temperature of the swirling airflow in the centrifugal separation chamber 20 is about 110 占 폚.

Next, the supply of the high-pressure gas is started toward the inside of the centrifugation chamber 20 of the classifier 4 using the blower 8. [ The high-pressure gas injected from the blower 8 is heated to a predetermined temperature by the first heater 10 (step S18). Similarly to the second heater 14, the first heater 10 heats the high-pressure gas so that the temperature of the swirl gas in the centrifugal separation chamber 20 is about 110 ° C. The high-pressure gas heated to a predetermined temperature is ejected from a plurality of ejection nozzles 30 provided on the outer peripheral wall of the centrifuge chamber 20 and supplied into the centrifuge chamber 20 (step S20).

As described above, when a state in which the high-speed swirling air heated to about 110 DEG C is normally rotated in the centrifugal separation chamber 20, the mixed powder quantitatively delivered from the feeder 6 is centrifugally separated from the inlet 26 And is introduced into the chamber 20 (step S22). 2, since the charging port 26 is provided above the outer peripheral portion of the centrifugal separation chamber 20, the mixed powder injected from the charging port 26 is circulated to the outer peripheral portion of the centrifugal separation chamber 20 at a high speed And is dispersed abruptly. At this time, the dispersant mixed in between the fine particles of the powder is rapidly vaporized, and dispersion of the powder is promoted. The powder dispersed in the particulate unit as described above is not adhered to the surfaces of the upper disk-like member 22 and the lower disk-shaped member 24 constituting the centrifuge chamber 20, And is classified on the basis of the particle size of the powder (step S24).

As a result of the centrifugal separation operation in the centrifugal separation chamber 20, the fine particles having a particle size smaller than the desired classification point are collected in the central portion of the centrifugal separation chamber 20, and the upper disc- (Step S26), together with the gas sucked by the suction blower 12, by the effect of the ring-shaped convex portion provided at the center of each of the first and second suction chambers 24, respectively. The coarse powder having a particle size exceeding the classification point is collected at the outer peripheral portion of the centrifuge chamber 20 by the centrifugal action in the centrifugal separation chamber 20, 4 and is discharged from the discharge port 34 and accommodated in the recovery container 16. [

As described above, the powder that is effectively dispersed by the effect of the high temperature swirling air circulating in the centrifugal separation chamber 20 and the effect of the preparation is not adhered to the upper surface of the components constituting the centrifugal separation chamber 20, It circulates in the yarn 20 and is efficiently classified into a fraction less than a desired classifying point and the remaining fraction. In addition, since the additives added are all vaporized, they are not included in the recovered powder.

In the present embodiment, the gas supplied to the classifier 4 is heated to about 110 DEG C, but the temperature of the swirler 4 in the classifier 4 is not limited to about 110 DEG C, So long as it is vaporized in the separation chamber 20.

In the present embodiment, water or glycols are used in the preparation, but ketones may be used as a preparation.

Next, a powder classification method according to a second embodiment of the present invention will be described with reference to the drawings. The structure of the powder sorting method according to the second embodiment is such that the mixing step of the powder sorting method according to the first embodiment is changed to be mixed while heating. Therefore, the detailed description of the same configuration as the classifying apparatus 2 described above will be omitted, and only the other portions will be described in detail. The same components as those of the classification device 2 described above are denoted by the same reference numerals.

5 is a flowchart for explaining a powder classification method according to the second embodiment. First, the powder to be classified and the preparation are mixed while heating (step S30). Here, the kind of the auxiliary agent to be used may be appropriately selected according to the kind of the powder to be classified. However, when the object to be classified is a powder of nickel, as in the method of classifying the powder according to the present embodiment, water or glycol It is preferable to use an organic solvent having a flash point of 80 DEG C or higher such as ethylene glycol (flash point 124 DEG C). At this time, in the present embodiment, the heating is carried out at about 75 캜, but the heating temperature may be appropriately selected depending on the combination of the powder and the auxiliary. Next, the processes shown in the steps S32 to S40 are executed, but these processes are the same as the processes shown in the steps S12 to S20 in the flowchart of Fig. 4, respectively, so that the description is omitted. Then, the mixed powder discharged quantitatively from the feeder 6 is introduced into the centrifugal chamber 20 through the inlet 26 (step S42). At this time, since the mixture is heated in step S30, the mixed powder is put into the centrifuge chamber 20 at a predetermined temperature. The processes shown in the steps S44 and S46 are executed. Since these processes are the same as the processes shown in the steps S24 and S26 in the flowchart of Fig. 4, the description is omitted.

The temperature of the swirling airflow in the centrifugal separator 20 can be set by, for example, heating the atmospheric pressure gas sucked so that the temperature of the swirling airflow is about 110 DEG C in step S34, The high-pressure gas is heated by the first heater 10 so that the temperature of the swirling airflow is also about 110 DEG C in step S40.

[Example]

Next, the powder classification method according to the present embodiment will be described in more detail with reference to examples. In this embodiment, the classifier equipped with the adiabatic equipment is used, the amount of gas sucked into the suction blower 12 shown in Fig. 1 is 0.5 m 3 / min, the pressure of the high-pressure gas generated by the blower 8 is 0.5 MPa. Further, in the present embodiment, as a powder to be classified, a powder composed of a fine powder of nickel (having a median diameter of 0.73 μm, a ratio of 1 μm or less to 79.5 vol%, maximum particle diameter of 3.3 μm) An organic solvent is added and mixed powder is used. In addition, the amount of powder added to the classifier was set at 500 g / hour. The temperature in the classifier is set at 110 캜. The temperature in the classifier is obtained by measuring the temperature of the gas immediately after being sucked from the suction port in the classifier by the suction blower of the classifier. Further, as described above, the auxiliary agent added to the powder partially evaporates during mixing with the powder and after mixing. Therefore, in this embodiment, the amount of the additive to be added when mixing the powder is referred to as the "additive amount", and the amount of the additive included in the mixed powder when the mixed powder is fed into the feeder 6 of the classifying device 2 as " Quot; adsorption amount ".

(Example 1)

In Example 1, water was used as a preparation, and water was added in an amount of 3 to 5% by mass relative to the nickel powder. Further, mixing of the nickel powder and water was carried out at 20 캜 and 75 캜. Table 2 shows the relationship between the amount of water added (mass ratio), product yield, and product quality in the mixed powder. Further, the product quality is data on nickel recovered from the suction port 32 shown in step S26 of the flowchart of Fig. 4 and step S46 of the flowchart of Fig. Further, as a comparative example, an experiment was also conducted in which the pretreatment of adding the auxiliary agent to the nickel powder was not performed.

Pretreatment method Product yield
(Dry matter)
[%] Product quality Types of preparation
Addition amount Temperature at mixing
(Powder temperature)
[° C] pharmacy
Absorption
[%]
Or less
ratio[%] Maximum diameter
[Mu m] Example
1-1 Water (3%) 20 2.7 27.6 94.4 2.3 Example
1-2 Water (3%) 75 2.0 23.6 95.8 2.0 Example
1-3 Water (5%) 75 3.2 22.9 95.1 2.3 Comparative Example
One No preprocessing 0 15.0 95.6 2.3 Comparative Example
2 none 75 0 16.5 95.6 2.3

As shown in Table 1, when the classification of nickel powder was carried out using water as a preparation, it was found that the product yield was higher than that in the case where the preparation was not added (Comparative Examples 1 and 2). It was also found that when the heating was carried out during mixing, the product quality was improved as compared with Comparative Examples 1 and 2. Further, experiments were conducted by adding water vapor in the centrifugal separation chamber 20 at the time of classifying without performing the pretreatment, but the increase of the product yield and the improvement of the product quality were not found.

Therefore, by using water as a preparation, the product yield of nickel can be increased, and furthermore, the product quality can be further improved by mixing the nickel powder and water while heating them.

(Example 2)

In Example 2, diethylene glycol was used as an example of an organic solvent having a flash point of 80 ° C or higher as a formulation, and diethylene glycol was added in an amount of 4% to 5% by mass relative to the nickel powder. Further, mixing of the nickel powder and diethylene glycol was carried out at 20 캜 and 75 캜. Table 2 shows the relationship between the addition amount (mass ratio) of diethylene glycol in the mixed powder, product yield, and product quality. The product quality is data relating to nickel recovered from the suction port 32 shown in step S26 of the flowchart of Fig. 4 and step S46 of the flowchart of Fig. A comparative example in which pretreatment was not performed as in Example 1 is also shown.

Pretreatment method Product yield
(Dry matter)
[%] Product quality Types of preparation
Addition amount Temperature at mixing
(Powder temperature)
[° C] pharmacy
Absorption
[%]
Or less
ratio[%] Maximum diameter
[Mu m] Example
2-1 Diethylene glycol
(4%) 20 3.7 29.9 93.2 2.3 Example
2-2 Diethylene glycol
(5%) 75 4.1 25.8 97.8 1.6 Comparative Example
One No preprocessing 0 15.0 95.1 2.3 Comparative Example
2 none 75 0 16.5 95.6 2.3

As shown in Table 2, it was found that when the nickel powder was classified using diethylene glycol (flash point 124 ° C) as a preparation, the product yield was higher than that in the case where the preparation was not added (Comparative Examples 1 and 2) . It was also found that the product quality was improved in comparison with Comparative Examples 1 and 2 when heating was performed at the time of mixing.

Therefore, by using diethylene glycol as a coagent, the product yield of nickel can be increased, and the product quality can further be improved by mixing the nickel powder and water while heating.

From the results of Examples 1 and 2, it was found that when the nickel fine powder, water and diethylene glycol were mixed as a preparation, the product yield of the nickel fine powder was increased and the classification efficiency was increased. Further, when the nickel fine powder and the auxiliary are mixed while heating, the product quality is further improved. In both of the above-described Examples 1 and 2, centrifugal separation was continued for 30 minutes, but the operation was not stopped due to occlusion.

As described above, according to the powder classification method according to each of the above-described embodiments, the powder made of nickel, which is the object to be classified, is mixed with water or a formulation comprising an organic solvent having a flash point of 80 ° C or higher, And at the same time, the heated gas forms a high-speed flywheel flow in the centrifugal separation chamber, so that classification of powders having a particle size of 1 μm or less can be efficiently performed. When the powder of nickel to be classified is mixed with water or a formulation comprising an organic solvent having a flash point of 80 DEG C or higher while heating, the viscosity of the preparation decreases due to heating, the powder and the preparation are further uniformly dispersed, It further improves.

2: classifier 4: classifier
6: Feeder 8: Blower
10: first heater 12: suction blower
14: second heater 20: centrifugal separator
22: upper disk-shaped member 24: lower disk-shaped member
26: Inlet port 30: Spout nozzle
32: inlet 40: guide vane

Claims (5)

A method of classifying a powder using a fluid classifier,
A mixing step of mixing a powder made of nickel and a preparation made of an organic solvent having a flash point of 80 ° C or higher;
An injecting step of injecting the powder mixed in the mixing step into the fluid classifier,
A heating step of heating the substrate,
A supply step of supplying the gas heated in the heating step to the fluid classifier,
And a classifying step of classifying the powder on the basis of the particle size while vaporizing the preparation mixed with the powder in the fluid classifier
Classification method of powders. The method of claim 1, wherein
Wherein the preparation is a glycol.
Classification method of powders. The method according to claim 1,
Characterized in that the preparation is a ketone
Classification method of powders. A method of classifying a powder using a fluid classifier,
A mixing step of mixing powders made of nickel and a formulation comprising water,
An injecting step of injecting the powder mixed in the mixing step into the fluid classifier,
A heating step of heating the substrate,
A supply step of supplying the gas heated in the heating step to the fluid classifier,
And a classifying step of classifying the powder on the basis of the particle size while vaporizing the preparation mixed with the powder in the fluid classifier
Classification method of powders. 5. The method according to any one of claims 1 to 4,
Wherein the nickel powder and the auxiliary powder are mixed while heating in the mixing step
Classification method of powders.

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