JPH0440226A - Apparatus for granulating particulate material - Google Patents

Abstract

PURPOSE:To obtain molded particles reduced in the width of particle size distribution and having high dimensional and configurational accuracy by supplying a slurry to an emitting nozzle from a supply means and generating pressure in the flow path of the nozzle in a pulsated state to form the droplet of the slurry and drying the emitted droplets of the slurry. CONSTITUTION:A slurry is supplied to an emitting nozzle 12 from a slurry container 10 through a supply pipeline. When voltage is applied to the heater 24 in the emitting nozzle 12 in a pulsated state in parallel to the supply of the slurry to suddenly heat the heater by the supply of a current, the slurry generates a bumping phenomenon at the part being in contact with the heater 24 and the boiling of a water membrane is generated. Generated in the flow passage of the slurry by said air bubbles. The slurry is injected in a liquid droplet state from the tip of the emitting nozzle by the action of this pressure. The liquid droplets are perfectly globular and dried during the passage through the drying chamber 18 within an electric furnace 16 to become solid particles.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a granulation device commonly used in industrial fields such as ceramics, foods, pharmaceuticals, and agricultural chemicals.

(Prior art) In industrial fields that handle fine powders, powders are granulated for various purposes. For example, in the ceramics industry, clay consisting of granules is dry press-molded to form desired shapes. In order to obtain the granules, the raw materials are pulverized and granulated to a certain particle size.

What shape do you want in this dry press molding? In order to obtain this, it is necessary that the granules be as homogeneous as possible and have high fluidity. In order for the granules to be homogeneous and have high fluidity, the shape of each particle must be close to spherical, and the width of the particle size distribution must be narrow.

For this purpose, a disk-type spray dryer has conventionally been generally used as a granulation device. FIG. 5 shows a schematic configuration of this device.
The high-speed rotation of the disk-shaped atomizer 102 causes the slurry to be scattered around by centrifugal force to form droplets, and together with this, heated air is ejected from the duct 104 to dry the slurry droplets and granulate them.

Each granulated particle is taken out from the outlet 108 at the lower end of the drying chamber 106.
The dust consisting of fine particles taken out from the drying chamber 106 and generated in the drying chamber 106 is collected by a collection device 110.

The granules obtained by this apparatus are different from those obtained by other types of granulation apparatus, such as a granulation apparatus using a transfer granulation method, a 2ML moving bed granulation method, or a granulation apparatus such as a nozzle-type spray dryer. Compared to granules, the particle shape is relatively close to spherical, the width of the particle size distribution is narrow, and the fluidity is excellent.

(Problem to be solved by the invention) However, the slurry before granulation is made up of extremely fine particles suspended in the liquid, and the viscosity changes over time and the flow rate decreases accordingly. It may fluctuate. Therefore, even in the case of granulation using the disk-type spray dryer, hollow particles or spherical granules with holes are likely to be formed.

Needless to say, such granules lead to non-uniformity of the molded body and ultimately reduce the quality of the product.

Furthermore, in the case of the above-mentioned disk type spray dryer, since the slurry is blown away by centrifugal force to form droplets, a large drying space is required.

In order to obtain a ceramic granule of approximately 1.0 m in diameter, a drying space with a circular cross section of at least 2 to 3 m in diameter is required. If the drying space is smaller than this, the scattered droplets will adhere to the wall surface of the drying chamber, resulting in an extremely low yield.

Furthermore, in the case of this spray dryer, since fine powder is inevitably generated in principle, a collection device is required from the viewpoint of pollution prevention and reduction of material loss, etc., making the entire device large-scale and increasing the cost of the device. .

(Means for Solving the Problems) The granulation device of the present invention has been devised to solve the above problems, and its gist is (a) circulating slurry and discharging it from the discharging section at the tip. A discharge nozzle for discharging, and (a
) a supply means for supplying the slurry to the discharge nozzle; and (c) generating pressure in a pulsed manner in the slurry flow path in the discharge nozzle to form the slurry into droplets and discharge it from the discharge part at the tip of the discharge nozzle. and a pressurizing means for drying and granulating the slurry droplets discharged from the discharge section.

(Operation and Effects of the Invention) As described above, the present invention generates pressure in the slurry flow path in the discharge nozzle in a pulsed manner, and discharges the slurry that is continuously sent in droplets from the tip of the nozzle. , which was dried. After the slurry droplets discharged from the nozzle tip are released into free space, they become spherical due to the action of surface tension.

It has been confirmed that in the granules obtained by the apparatus of the present invention, each particle is almost perfectly spherical, and the width of the particle size distribution is narrow. Therefore, when dry press molding is performed using the granules obtained by the apparatus of the present invention, the granules have high fluidity and are homogeneous.

A molded article with high dimensional accuracy and shape accuracy can be obtained.

In addition, unlike conventional disk-type spray dryers, which use centrifugal force to turn slurry into droplets, the slurry is turned into droplets by pulse-like pressure generated within the flow path, so it requires a large drying space. Therefore, the device can be configured compactly and the cost is low.

(Example) Next, an example of unreleased IJl will be described in detail based on the drawings.

In FIG. 1, 1o is a slurry (mud vI) supply container;
12 is a discharge nozzle, and the discharge nozzle 12 from the supply container 10
A jF 14 is provided on the supply pipe to.

16 is an electric furnace having a drying chamber 18 inside.

20 is a collection container for granules.

The discharge nozzle 12 has a slurry passage 22 inside, and a heater 24 is disposed on the inner wall surface of this passage 22. A pulsed voltage is applied to the heater 24.

Next, the operation of forming slurry into droplets, drying, and granulating using this apparatus will be explained.

Slurry is stored in a slurry container 10 and is supplied to a discharge nozzle 12 through a supply conduit. At the same time, a voltage is applied in a pulsed manner to the heater 24 in the discharge nozzle 12 to rapidly energize and heat it.

Then, as shown in FIG. 2(B), the slurry undergoes a bumping phenomenon at the portion in contact with the heater 24, causing a water film to boil. The generated bubbles 23 eventually grow into large bubbles 26 as shown in Figure CC), thereby generating pressure within the slurry flow path.

Due to the action of this pressure, the slurry is transferred to the discharge nozzle 1.
It is turned into droplets and ejected from the tip of 2 (see figure (D)).
When the ejected droplets are released into free space, they take on a nearly perfect spherical shape due to the action of surface tension, and then the ejected droplets form a nearly perfect sphere.
While passing through the drying chamber 18 inside, the particles are dried and become solid particles, which are collected in the collecting container 20 below.

On the other hand, the bubbles generated within the discharge nozzle 12 are cooled down and become smaller when the power supply to the heater 24 is stopped, and eventually disappear. Then, new slurry is continuously supplied from the supply container 10, and the heating by energization of the heater 24, the generation of bubbles thereby, the generation of pressure, the resulting dropletization of the slurry, and the discharge from the nozzle 12 are repeated one after another.

In the case of this apparatus, the resulting granules have a narrow particle size distribution and excellent fluidity. In addition, the granules have a nearly spherical shape and a high bulk specific gravity.

Furthermore, this device has a simple device configuration, and droplet formation can be easily controlled electrically! ! (Conventional disc-type spray dryers control droplets by controlling the rotation speed of the atomizer, and nozzle-type spray dryers control droplets by controlling flow rate, but neither is easy.)
In addition, it has the advantage that it is easy to produce in small quantities, and even if mass production is required, it can be easily handled by increasing the number of discharge nozzles.

[Experiment example] Next, the results of the experiments conducted will be explained in detail.

(a) Fabrication of the discharge nozzle As shown in Figure 3 (^), a transparent quartz glass plate 28 with a thickness of 2mm, a width of 10ts, and a length of 30m5 is
A groove 30 having a length of 207 zm, a depth of 70 ILm, and a length of 3 cm was formed by an etching method using hydrofluoric acid water. Furthermore, platinum was sputtered onto a glass plate 29 of the same size in the pattern shown in FIG. 3A to form a platinum thin film 32. This platinum
The iI film 32 was formed at a position retracted approximately 1.0 cm from one end of the quartz glass plate 29 in the longitudinal direction. The pattern shape is such that the thickness of the thin film is approximately 0.3 pm, and d+ = l
Oml.

d, = 1.5 ms, d, = 0.51 @, d, = 4.5 鳳■, d, = 1.0 Enkaku.

Next, a part of the quartz glass plate 28 on which the groove 30 was previously formed is cut out, the cutout part 34 is used for taking out the electrode, and this glass plate 28 is attached to another glass plate as shown in FIG. 29 and bonded with epoxy adhesive.

Furthermore, a lead wire 36 is attached to the platinum 5S32 electrode using conductive resin.
A discharge nozzle 40 was manufactured by connecting the silicon tube 38 for slurry supply and covering the slurry supply end side of the quartz glass plate 28, 29 in sufficient tightness. Note that the other end of this silicone tube 38 is connected to the supply container side. Furthermore, the lead wire 36 is connected to a power source.

Note that the thin platinum W132 has a narrow width at the center and a high resistance, so heat is generated here due to Joule heat, that is, this narrow portion acts as a heater. Here, a pulsed voltage generator whose output voltage and pulse intensity can be arbitrarily adjusted was used as the power source.

(b) Preparation of Slurry Calcium carbonate, talc, kaolin, etc. were added to alumina powder AL160SG manufactured by Showa Light Metal Co., Ltd., and an alumina slurry with a purity of 96% was prepared by a wet ball milling method. Here, wood is added to the slurry so that the slurry concentration is about 45% of solids (solid content concentration), and PVA is added as an organic additive.
, 4% PEG and 1% polycarboxylic acid ammonium salt as a deflocculant were added, and wet ball milling was performed. The slurry viscosity at this time was about 100 cp during the series of experiments.

(c) Granulation experiment Using the apparatus shown in FIG. 4, approximately 100 mJ1 of the slurry prepared as described above was poured into the supply container IO, the lower valve 14 was opened, and the container IO was placed at a position slightly higher than the discharge nozzle 40. , the slurry was set just before it would flow out from the spout of the discharge nozzle 40.

Next, cooling water for cooling the nozzle 40 was flowed, and heated air was sent into the drying chamber 46 of the droplet drying device 44 from the inlet 42. At this time, the temperature of the heated air near the air inlet 42 was set to about 200°C. did.

Here, a 50 V, 10.5 rectangular pulse was generated at a frequency of 200 Hz using a pulse generator.

The platinum heater of the discharge nozzle 40 was energized. Then, the platinum heater generated heat and bubbles were generated at the solid-liquid interface in contact with the alumina slurry, and the resulting pressure caused the slurry to be ejected from the discharge nozzle 40 in a drip-like manner, forming continuous droplets. The droplets immediately dried while flying through the drying chamber 46 to form spherical granules, which were collected in a collector 48 at the bottom of the apparatus.

When the properties of the obtained granules were examined, they were 1! It looked like the i4i table.

(Left below) t! Table 41 When the properties of the obtained granules were examined, they were as shown in Table ff12.

Table 2 shows that the amount of solids contained in the dry air flowing out from the air outlet 50 was almost negligible.

This granule was dry press-molded at loOMPa to prepare pellets with a diameter of 20 m5φ and a height of about 51 mm.
When baked at 0°C for 1 hour, the bulk density was 3.88. A fired body with a water absorption rate of 0.0% was obtained.

(d) Comparative Experiment The same alumina slurry as above was poured into a commercially available disk type spray dryer, and granulated by spray drying with heated air at 200°C.

Although the embodiments of the present invention have been described in detail above, these are merely examples of the present invention, and the present invention can be constructed with various modifications based on the knowledge of those skilled in the art without departing from the spirit thereof. It is possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of a granulation device that is an embodiment of the present invention, FIG. 2 is an explanatory diagram of its operation, FIG. 3 is an explanatory diagram of the configuration of a discharge nozzle manufactured for the experiment, and FIG. The figure is an explanatory diagram of the configuration of the experimental apparatus, and FIG. 5 is a schematic diagram of the configuration of a conventional disk type spray dryer. lO: Supply container 12, 40: Discharge nozzle 16: Electric furnace 18: Drying chamber 20: Collection container 22: Passage 24: Heater

Claims (1)

[Claims] (a) a discharge nozzle that circulates slurry and discharges it from a discharge portion at the tip; (b) a supply means for supplying slurry to the discharge nozzle; and (c) pulses pressure within the slurry flow path in the discharge nozzle. and a pressurizing means for generating the slurry in the form of droplets and discharging the slurry from the discharge part at the tip of the discharge nozzle, and drying and granulating the slurry droplets discharged from the discharge part. Powder granulation equipment.