JPH11319535A - Throttling disk for particle-coating apparatus, apparatus for coating particle comprising throttling disk, and method for coating particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throttling disk for a particle-coating apparatus capable of preventing pulsation of a jet gas and a particle, evenly forming a coating on the surface of the particle, inhibiting the particle from aggregating in throttling parts, and possible to be manufactured by industrial mass production and to provide an apparatus for coating a particle and a method for coating a particle. SOLUTION: This throttling disk 52 for a particle-coating apparatus and produced by evenly forming a prescribed number of jetting holes 56 in a disk 54 as to control the aperture ratio of 10-70% is employed for a throttling part of a jetting tower. The throttling disk 52 is fitted to a lower part of a jetting tower while a coating liquid-jetting nozzle 26 being inserted into at least one of the jetting holes 56.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drawing disk for a particle coating apparatus, a particle coating apparatus provided with the drawing disk, and a method for coating particles using the apparatus. More specifically,
Forming a spouted bed of granules in a tank, spraying a coating liquid on the spouted bed, and coating the granules with a film; a drawing disk for a granule coating device; a coating device using the same; and a granule coating using the same device About the method.

[0002]

2. Description of the Related Art As a method of coating particles using a jet flow method, for example, as described in Japanese Patent Publication No. 38-13896, the lower part of a cylindrical tank is formed in an inverted conical shape, and the lower end side is horizontally oriented. Into a narrowed portion for gas jetting, and a high-speed gas stream is jetted vertically upward into the tank through the narrowed portion to blow up particles to be coated in the tank, and simultaneously spray particles with the coating liquid. This is a method of coating the body with a coating. Tokiko 38
No. 2294 discloses a method in which the particles are blown up through a guide tube provided in a central jet portion in a jet tower, and a coating liquid is sprayed from a spray nozzle provided in the tube. In Japanese Patent Publication No. 50-1355, a guide tube is provided in the jet part, and gas is also passed around the jet part, so that the granules can be flowed.
Alternatively, it is placed in a weightless state close to the above, thereby avoiding troubles such as adhesion of the particles.

[0003] All of these coating methods are intended for coating pharmaceuticals, and are preferable methods for small-scale and gentle coating. However, when it is necessary to coat a large amount at low cost, for example, when a fertilizer or the like is to be coated, this method is not an appropriate method. When coating a large amount of particles, it is necessary to use a jet tower having a large diameter. However, when the diameter of the jet tower is large, the whole particles are in a flowing state, and there is a problem that a spouted bed cannot be formed.

To solve this problem, Japanese Patent Publication No. 2-3939
Discloses a technique in which a jet state can be obtained even when a jet tank becomes large. In other words, in order to produce and supply a large amount like fertilizer, a coating device in which a guide tube is provided vertically above an orifice in a jet device using a large-diameter jet tower is used. When introducing the active gas, the flow velocity of the gas at the orifice is set to 20 m / sec or more.
70 m / sec, and the flow velocity in the guide tube is 20 m / sec.
The coating is performed by adjusting the value to c or less.

On the other hand, recently, JP-A-6-9303, JP-A-6-9304, JP-A-6-72805, JP-A-6-80514, JP-A-5-29634 and JP-A-5-29634 have recently been disclosed.
As disclosed in JP-A-202078, JP-A-4-202079 and JP-A-6-87684, the active ingredient is not eluted for a certain period after fertilization or the period in which the elution is extremely suppressed (this period is referred to as A coated granular fertilizer in which the surface of a fertilizer granule is coated with a coating having a so-called timed elution type pattern having an initial dissolution period) is disclosed.

[0006] The coated granular fertilizer in which the surface of the fertilizer granules is coated with a coating having such a time-dissolved elution pattern is applied to the fertilizer granules by using a jet tower as described in JP-B-2-31939. In the case of inexpensive, large-scale production, the method of attaching the coating resin solution to the granules, the scattering of the solvent from the adhered resin solution, and the state of drying are affected by the production efficiency and the active ingredient of the obtained coated granule fertilizer. It is thought to have a significant effect on the elution pattern.

When a large amount of coated granular fertilizer is produced using a large spout tower, it is considered important to shorten the drying time in order to economically increase the production efficiency, and the drying time is conventionally shortened. For this reason, it is often attempted to increase the supply amount of the resin solution and to scatter and dry the solvent contained in the resin solution attached to the surface of the granules using a large amount and high-temperature jet gas.

However, when using a jet tower to coat particles having a relatively low melting point, such as urea particles, the temperature of the jet gas must be kept below the melting point of the urea particles. Therefore, the production efficiency cannot be increased by using a high-temperature jet gas. That is, when coating is performed with the temperature of the jet gas being equal to or higher than the melting point of the urea granules, uneven scattering and drying of the solvent occur in the jet tower, and therefore, the annular urea granules formed outside the guide tube are formed. A part of the urea particle deposition layer (fixed layer) is melted and solidified, and the urea particles are melted and solidified into the gas jet throttle at the inverted conical tip at the bottom of the tower. In some cases, uniform circulation cannot be performed, and substantial operation cannot be performed.

When the temperature of the jet gas is kept below the melting point of the urea particles to increase the amount of the jet gas, the amount of the particles sent from the lower part of the jet tower to the guide tube fluctuates, causing a so-called pulsation phenomenon. The operation becomes unstable. In this case, the coating film of the urea granules is liable to be damaged, and the obtained coated fertilizer has a large amount of active ingredient eluted during the initial elution suppression period. That is, many of the obtained coated fertilizers rapidly elute the active ingredient immediately after fertilization. Therefore, it is extremely difficult to produce a large amount of time-dissolved coated fertilizer having a desired dissolution function by a conventional jet method with high production efficiency.

[0010] Further, the conventional diaphragm is as shown in FIG.
A so-called donut-shaped gas ejection body 84 called an orifice having an ejection hole 82 formed in the center of the disk 80 is provided at the tip of the inverted cone at the bottom of the tower. There is also a problem that the coated particles falling down in the tower are deposited on the upper surface of the gas ejector 84 and melted and solidified.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present inventors have sought to find out where the cause is. As a result, in the jet method, when the temperature of the jet gas is set to be equal to or higher than the melting point of the urea granules to coat the surface of the urea granules, even if the spray of the resin solution covering the urea granules is uniform, the jet gas and urea It has been discovered that pulsation of the granules occurs, causing a portion where the temperature of the jet gas does not partially decrease due to the heat of vaporization of the solvent, thereby melting and consolidating the urea granules by the high-temperature jet gas.

Furthermore, even if the temperature of the jet gas is kept below the melting point of the urea granules, increasing the jet amount of the jet gas causes a drift in the jet gas, so that the amount of the granules sent to the guide tube is reduced. It was discovered that a fluctuating, so-called pulsation phenomenon occurred, and that the coated urea particles collided with the upper wall of the spout tower and damaged the coating of the coated particles.

Further, it has been found that the fusion of the particles to the narrowed portion is one of the causes of the above-mentioned problem.

The present invention has been made on the basis of the above findings, and has as its object to prevent the pulsation of the jet gas and the granules, to maintain a uniform and stable jet state, and thus to uniformly form the granules. It is possible to coat the surface with a coating, further prevent the particles from being fused to the drawn portion, and to industrially mass-process the drawn disk for a coating device for the granular material, the granular material provided with the drawn disk. An object of the present invention is to provide a coating apparatus and a method for coating granules.

[0015]

In order to achieve the above-mentioned object, the present invention provides: [1] A predetermined number of ejection holes are uniformly formed mainly in a disk, and the opening ratio is 10 to 70%. A throttle disk for a coating apparatus for a granular material, wherein a coating liquid spray nozzle is inserted into at least one of the ejection holes of the throttle disk and attached to a lower part of a jet tower, and a jet tower is provided from a lower part of the jet tower through the jet hole. A particle formed by spraying a gas into the spout tower to form a spouted layer of particles in the spout tower, and spraying a coating liquid from the nozzle onto the particles forming the spouted bed to coat the particles with a coating film The present invention proposes a throttle disk for a coating apparatus for granular material, which is attached to a lower portion of a jet tower of a coating apparatus and ejects gas into the jet tower.

The present invention also provides [2] a granule coating apparatus to which the drawing disk according to the above [1] is attached. [3] The coating apparatus according to [2], This includes the case where the tower has a guide tube whose axis is vertically mounted in the tower.

The present invention further provides: [4] A predetermined number of ejection holes are uniformly formed mainly in a disk, and the opening ratio thereof is 10 to 10.
A 70% throttle disk is attached to the lower part of the jet tower, and a spray nozzle is inserted into at least one of the ejection holes of the throttle disk, and a guide pipe is provided vertically above the spray nozzle and in the jet tower. Using a granule coating apparatus having a spout tower provided, a gas is spouted into the spout tower through the spout hole of the throttle disk to form a spouted bed of granules in the spout tower, and the spouted bed is formed. A method for coating granules, comprising spraying a coating liquid from a spray nozzle onto the granules to be formed, and coating the granules with a coating.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of a granule coating apparatus according to the present invention. In FIG. 1, reference numeral 2 denotes a vertically installed jet tower. The main part of the jet tower 2 is constituted by a cylindrical tank main body 4.

The shape of the tank main body 4 is not particularly limited, and the shape of the horizontal section may be circular or polygonal. However, from the aspect of uniformity of circulation of the particles in the tank main body 4, it is desirable that the cross section of the tank main body 4 is circular.

A cylindrical guide tube 6 is attached to the inside of the tank main body 4 by fixing means (not shown).

The shape of the guide tube 6 is not limited to a cylindrical shape, but may be a hole formed in a pipe or a wire mesh formed in a cylindrical shape. The shape and material of the guide tube 6 are not particularly limited. However, if it is desired to minimize damage to the coating at the time of coating, a smooth pipe without holes or protrusions, or a fluororesin is applied to the inner surface of the pipe. It is preferable to use a lining. The guide tube 6 is fixed or suspended in the tank main body 4 above the throttle unit 10 with the axial direction of the guide tube 6 being vertical.

The lower portion of the tank body 4 has an inverted conical bottom 8 whose inner diameter is gradually reduced toward the bottom, and a narrowed portion 10 having a smaller diameter than the tank body 4 penetrating through the lower end of the bottom 8. Is formed. The orifice section 10 may be configured so that various orifice plates or venturis can be inserted separately.

One end of an extraction pipe 12 is connected to the restricting section 10, and the other end side is formed as a coating particle extraction port 16 through an on-off valve 14. One end of a gas supply pipe 18 is connected to the extraction pipe 12, and the other end of the gas supply pipe 18 is connected to a blower 22 via a gas heater 20 in the middle. As a result, the gas supplied from the blower 22 is heated by the gas heater 20 and then jetted into the tank main body 4 through the throttle unit 10. Reference numeral 24 denotes a flow meter interposed in the gas supply pipe.

The gas used in the present invention is not particularly limited as long as it is inert to the particles and the solvent. Specific examples include air, nitrogen gas, helium gas, and a recycle gas in which the organic solvent in the coating liquid is partially removed from the outlet gas of the jet tower.

A spray nozzle 26 is provided near the center of the throttle unit 10. The spray nozzle 26 is connected to the throttle unit 1.
It suffices if it is in the vicinity of the throttle unit 10 along the central axis direction of 0, and may be a position higher or lower than the throttle unit 10. The position and shape of the spray nozzle 10 are appropriately determined depending on the properties of the spray liquid, operating conditions, and the like.

The spray nozzle 26 is connected to one end of a coating liquid supply pipe 30 provided with a coating liquid supply pump 28, and the other end of the coating liquid supply pipe 30 is connected to a coating liquid preparation tank 32.
Connected to. The coating liquid prepared in the coating liquid preparation tank 32 is supplied to the coating liquid supply pipe 30 by the coating liquid supply pump 28.
Through the spray nozzle 26 and then sprayed into the tank body 4. Reference numeral 34 denotes a steam heating jacket.

Numeral 36 denotes a granule input port formed in the tank main body 4, through which the granules are supplied into the tank main body 4.
The spouted layer 37 is formed, and the film is coated on the surface of the granular material. In addition, 38 is a granule inlet valve and 39 is a granule.

Reference numeral 40 denotes a discharge pipe attached to the upper wall 42 of the tank main body 4, through which gas in the tank main body 4 is discharged to the outside.

Reference numeral 44 denotes a particle deposition layer formed by depositing particles that have fallen on the peripheral edge portion 46 of the jet part.

FIG. 2 shows an example of the drawing disk 52 attached to the drawing section 10 in FIG. The aperture disk 52 is provided with a predetermined number (four in this figure) of ejection holes 56 having a center on a concentric circle centered on the center of the disk main body 54 and spaced substantially at equal intervals from each other. By uniformly piercing the jet holes 56 in the disk main body 54 at substantially equal intervals on a concentric circle, the gas passing through each jet hole 56 can be jetted uniformly into the jet tower.

In FIG. 2, four ejection holes 56 are formed. However, the invention is not limited to this, and any number of two or more ejection holes can be formed. 10
It is practically preferable to make the number. Further, in FIG. 2, the ejection holes 56 are formed on concentric circles. However, for example, a grid-like grid point, a staggered shape, or any other arrangement can be adopted, that is, the ejection holes 56 are uniformly formed on the disk main body 54. What is necessary is just to arrange | position so that the gas which passes through each ejection hole may be ejected uniformly into a jet tower.

The opening ratio of the ejection holes 56 with respect to the disk main body 54, that is, the following formula (1): Opening ratio (%) = (total area of injection holes / area of disk main body before perforation) × 100 (1) The aperture ratio is preferably from 10 to 70%, particularly preferably 2 to 70%.
0-60% is preferred. If the aperture ratio is less than 10%,
The particles are easily deposited and solidified on the upper surface of the drawing disk. On the other hand, if the aperture ratio exceeds 70%, the throttle effect of the throttle portion becomes insufficient, and it tends to be difficult to obtain a sufficient gas jet velocity.

When the throttle disk 52 is attached to the throttle section 10 of the jet tower, as shown in FIG.
The diaphragm disk 52 is attached to the diaphragm unit 10 horizontally so that the hole passes through the center of the ejection hole 56. By attaching the throttle disk 52 in this manner, the gas supplied from the blower 22 is ejected into the tank main body 4 through the gap 60 between the disk main body 54 and the coating liquid supply pipe 30 or the spray nozzle 26. .

In FIG. 2, the spray nozzles 26 are provided for each of the ejection holes. However, the present invention is not limited to this. As shown in FIG.
a and 56b may be provided. Also in this case, the spray nozzle 2
6 are preferably arranged as uniformly as possible in the disk main body 52.

The gas flow velocity in the throttle unit 10 is determined by the amount of gas ejected and the throttle diameter. Further, the gas flow velocity in the guide tube 6 can be calculated by the same method. It is preferable that the distance between the guide tube 6 and the constricted portion 10 be selected within a range that does not hinder the circulation of the particles. The diameter of the guide tube 6 is preferably 1.2 to 4 times, more preferably 1.5 to 3 times, the diameter corresponding to the total area of the ejection ports 56 formed in the throttle disk 52. In the present invention, the gas flow rate in the throttle unit 10 and the gas flow rate in the guide tube are not particularly limited, but in order to stabilize the quality, an inert gas is sent from the throttle unit 10 into the apparatus. At this time, the flow rate of gas at the jet port 56 formed in the throttle disk 52 is
A method is recommended in which the coating is performed by adjusting the flow velocity of the gas in the guide tube 6 to 0.5 to 3 times the terminal velocity of the circulating particles at 0 m / sec.

In the coating apparatus of the present invention, the granules to be coated are not particularly limited. However, the coating by the coating apparatus of the present invention requires the control of the elution rate of the active ingredient contained in the granules. Particularly effective for the body. The active ingredient varies depending on the purpose and use of the active ingredient. Iron, boric acid, borax, manganese sulfate,
Manganese chloride, zinc sulfate, copper sulfate, sodium molybdate, ammonium molybdate, OMUP (clotilidene diurea), IBDU (isobutylidene diurea)
And pesticides such as insecticides, fungicides, herbicides, and the like. The granules may be granules of one or more active ingredients, and further granules comprising one or more active ingredients and an inert carrier such as bentonite, zeolite, talc, clay, diatomaceous earth and the like. Is also good. Furthermore,
The above-mentioned active ingredient particles may be coated with a resin or an inorganic substance.

The particle size of these particles is not particularly limited,
It is preferably from 0.1 to 10 mm, particularly preferably from 1 to 5 mm.

In the coating apparatus of the present invention, the coating material used for coating the granules is not particularly limited. However, in the case of producing time-eluting coated granules, the elution of the active ingredient contained in the granules is required. What is necessary is just to select the material and composition of which can control strictly. As such a coating material, an inorganic coating material represented by sulfur, an alkyd resin, a phenol resin,
Examples include thermosetting resins such as epoxy resins, polyolefins such as polyethylene and polypropylene, and thermoplastic resins such as polyvinylidene chloride.

Of these, thermosetting resins and thermoplastic resins are used as coating materials when coating granules containing active ingredients that require strict and long-term dissolution control, such as fertilizers and agricultural chemicals. It is preferable to use a thermoplastic resin if more sophisticated elution control is required.

Preferred thermoplastic resins include polyolefins and copolymers thereof, and polyvinylidene chloride and copolymers thereof. Preferred polyolefins and copolymers thereof are polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / propylene.
Vinyl acetate copolymer, ethylene / carbon monoxide copolymer,
Ethylene / vinyl acetate / carbon monoxide copolymer, ethylene / acrylate copolymer, ethylene / methacrylic acid copolymer, rubber resin, polystyrene, polymethyl methacrylate, etc. Examples of the copolymer include polyvinylidene chloride, vinylidene chloride / vinyl chloride copolymer, and the like. Further, biodegradable polyesters represented by poly-2-hydroxy-2-alkylacetic acid, poly-3-hydroxy-3-alkylpropionic acid and the like can also be mentioned.

These coating materials may be dissolved in an organic solvent and sprayed on the granules in a jet state in a jet tower to perform coating, or may be sprayed in a molten state. It is particularly effective in a film forming method in which a film is formed by using a poor solvent solution of the above resin, spraying the solution onto granules and instantaneously drying the granules. In the case of instantaneous drying using a poor solvent for the above resin, a combination of a resin and an organic solvent having a property of dissolving at a high concentration when heated, and precipitating and forming a jelly-like resin when cooled is preferable. Since the film formed by this combination forms a very dense film, it is particularly suitable for forming a time-eluting film.

As a coating material other than the above, an inorganic filler represented by talc, a surfactant or the like can be used. These coating materials are dissolved / dispersed or melted / dispersed in a solvent, sent to a spray nozzle, and shared with the coating.

In the above description, the apparatus for coating a granular material having a jet tower provided with a guide tube 6 in the tank main body 4 has been described, but the present invention is not limited to this. The present invention includes an apparatus for coating a granular material having a jet tower without a guide tube. In this case, the above description is similarly applied.

Further, the granule coating apparatus of the present invention can be used as it is as a granulation apparatus.

[0046]

The present invention will be specifically described below with reference to examples and comparative examples.

1. Coating Apparatus The coating apparatus used in Examples and Comparative Examples is shown in FIG. 1, and the drawing disks used are shown in FIGS. 2 (Example) and 4 (Comparative Example).

The inner diameter of the jet tower 2 of the coating apparatus is 600 mm,
The height was 5000 mm. The guide tube 6 had a diameter of 150 mm and a length of 880 mm. The throttle disk used in the example had a diameter of 154 mm, an inner diameter of the ejection hole 56 of 45 mm, the number of ejection holes 4 (opening ratio 34%), and an ejection nozzle provided at the center of each ejection port 56. The ejection nozzle 26 was arranged on a circle having a diameter of 95 mm centered on the center of the drawing disk.

The drawing disk used in the comparative example had a diameter of 1 mm.
54 mm, inner diameter 95 mm of spout 82 (opening ratio 38%)
It was.

2. Coating Method Using a blower 22, a predetermined amount of particles was injected from the particle input port 36 while sending air maintained at a predetermined air volume and temperature to the jet tower 2. Next, when the temperature of the particles in the tower reaches 70 ° C., the coating liquid supply pump 28 is operated to activate the coating liquid preparation tank 3.
The coating liquid in 2 was sent to the spray nozzle 26 at a predetermined speed for a predetermined time to spray the coating liquid, and the coating rate was adjusted to a predetermined rate. After that, the blower 22 was stopped and the coated particles were extracted from the coated particle extraction port 16. .

Table 1 shows the operating conditions and results of the coating apparatus when the urea granules were coated. The coverage is 12% by weight.

In Comparative Examples 1 to 3, the value of "after 24 hours of dissolution rate" (initial dissolution rate (%)) increased remarkably as the gas temperature and the air flow rate increased. In addition, pulsation occurs in the “jet state”, and furthermore, “the presence or absence of melting and solidification in the tower”
About, there was melting and consolidation.

On the other hand, in Examples 1 to 4, the value of "after 24 hours of elution rate" was low regardless of the gas temperature and the air flow rate. In addition, no pulsation was observed in the “jet state”, and no melting / consolidation was observed in “presence of melting / consolidation in the tower”.

The coating solution had the composition shown in Table 2 below.
The solution at 0 ° C. and the coated granules are urea shown in Table 3.

[0055]

[Table 1] W: Input amount of urea particles into the jet tower Q: Flow rate of jet air T: Gas temperature at the inlet of the throttle unit u ₀ : Air flow rate at the outlet of the throttle disk Elution rate After 24 hours: 25 ° C, After 24 hours Dissolution rate of water in water (coated granules 10g, water 200ml)

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

As described above, in the drawing disk for a coating apparatus of the present invention, a predetermined number of ejection holes are uniformly formed mainly in the disk as described above, so that particles are deposited on the drawing disk and melted and consolidated. And jetting the jet gas uniformly and smoothly into the jet tower. For this reason, the operation of the apparatus is stable, and a large amount of coated granules can be stably manufactured. Therefore, when time-eluting type coated granules are produced using this apparatus, the obtained coated granules have stable elution, and in particular, have a stable initial elution suppression period determined by the coating composition. Can be manufactured in large quantities at one time. Further, the coating apparatus of the present invention can be provided with a guide tube in the tank main body. In this case, a more stable time-eluting type coated granule can be easily produced.

Further, the apparatus of the present invention is applicable to a case where it is necessary to uniformly coat a polyolefin film on the surface of a granular material,
This is particularly effective when a poor solvent such as polyolefin is used as a solvent for the coating material.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of the configuration of a granule coating device of the present invention.

FIG. 2 is an enlarged plan view showing an example of a drawing disk for a granule coating device of the present invention.

FIG. 3 is an enlarged plan view showing another example of a drawing disk for a particle coating apparatus according to the present invention.

FIG. 4 is a plan view showing an example of a conventional drawing disk for a particle coating apparatus.

[Explanation of symbols]

 2 Jet Tower 4 Tank Main Body 6 Guide Tube 8 Bottom 10 Throttle Section 20 Gas Heater 22 Blower 26 Spray Nozzle 32 Coating Liquid Preparation Tank 52 Throttle Disk 54 Disk Main Body 56 Spouting Hole 60 Gap

Claims (4)

[Claims] 1. A drawing disk for a coating apparatus for a granular material, wherein a predetermined number of ejection holes are uniformly formed mainly in a disk, and the opening ratio of the ejection holes is 10 to 70%. The coating liquid spray nozzle is inserted into at least one of the jet towers and attached to the lower part of the spout tower. Gas is jetted from the lower part of the spout tower through the jet hole into the spout tower to form a spouted layer of granular material in the spout tower. At the same time, the coating liquid is sprayed from the nozzle onto the granules forming the spouted bed and the granules are coated with a coating film. A squeezing disk for a coating apparatus for granular material, characterized in that the squeezing disk is used. 2. A granule coating apparatus to which the drawing disk according to claim 1 is attached. 3. The apparatus for coating granules according to claim 2, further comprising a guide pipe which is vertically mounted in the jet tower. 4. A predetermined number of ejection holes are uniformly drilled mainly in a disk, and a throttle disk having an opening ratio of 10 to 70% is attached to a lower portion of the jet tower, and a discharge hole of the throttle disk is formed. Insert a spray nozzle into at least one of the spray nozzles, and use a granule coating device having a jet tower provided with a guide tube vertically above the spray nozzle and inside the jet tower, and passing through the jet hole of the throttle disk A gas is blown into the spout tower to form a spouted layer of particles in the spout tower, and the particles forming the spouted bed are sprayed with a coating liquid from a spray nozzle to coat the granules with a coating. A method for coating granules, characterized in that: