JPH062632B2 - Method for preventing solidification of particulate hygroscopic fertilizer material - Google Patents

Description

TECHNICAL FIELD The present invention relates to prevention of solidification of a particulate hygroscopic fertilizer substance.

More specifically, the present invention relates to a method for preventing the solidification of particulate hygroscopic fertilizer material by coating fine particles of fertilizer with wax and further adhering fine particles of hydrous silicic acid.

2. Description of the Related Art Hygroscopic fertilizer materials include lime superphosphate, ammonium monophosphate, ammonium salt, urea, etc., but a large-grain urea will be described below as an example.

Large-sized urea has a particle size of 2 mm or more (usually 2 to 5 mm) and is manufactured for the purpose of increasing the nitrogen content of bulk blended fertilizer and reducing the manufacturing cost compared to chemical fertilizer by only physical mixing. However, in recent years, the demand has been increasing due to the demand of consumers.

However, since urea is originally highly hygroscopic and deliquescent,
It is inconvenient for storage, packing, transportation, and handling, and has a serious problem of solidification over time.

As a method for preventing the solidified particulate fertilizer substance having a high hygroscopic property, a method of coating with paraffin wax is well known and has been proposed for a long time.

Problems to be Solved by the Invention The method of coating with paraffin wax has major problems. It is that paraffin and urea react with each other to form an adduct in a treatment where the temperature of coated particles is high, generally at 65 ° C. or higher. Therefore, it is not preferable to increase the particle temperature, and usually the particle temperature of 30-
The coating treatment is performed by holding at 65 ℃, preferably 40-55 ℃
It is necessary to lower it to the processing.

Therefore, the melting point of the wax used must be such that it can sufficiently coat the particle surface at the coating treatment temperature. That is, those with a high melting point crystallize rapidly on the particle surface,
As a result, the particles are only partially covered with the protective film and immediately absorb moisture and deliquesce and congeal.

Also, if the melting point of the wax is too low, the surface of the particles is completely covered and the moisture resistance is excellent, but the particles become cohesive due to the softening of the wax, especially when the summer temperature rises, the tendency becomes remarkable, There is no coating method that can provide moisture resistance and anti-binding property, such as some handling is required during storage or packaging of flexible container bags. Usually, the coating treatment is performed with an emphasis on the anti-caking property even if the moisture-proof property is slightly inferior.

Further, researches using finely powdered inorganic compounds for preventing moisture and solidification of particulate hygroscopic fertilizer substances have been conducted. For example, diatomaceous earth, clay, gypsum, bentonite, porcelain earth, aluminum hydroxide, silicic acid, silicates such as magnesium and calcium carbonate are used, and silicate-based anti-caking agents such as diatomaceous earth and talc are most common.

However, these anti-caking agents need to be used in an extremely large amount in order to obtain a sufficient effect by themselves. Therefore, coloring occurs, and it takes a long time to perform the intended treatment, which is extremely difficult to carry out industrially,
Further, during handling, there are problems that the dust becomes violent and the environment is deteriorated, and that it adheres to the inside of the device. In addition, although the anti-caking effect is achieved, it has many drawbacks such that it is not hygroscopic and cannot maintain its effect for a long time.

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to solve the above problems and completed the present invention.

That is, according to the present invention, spherical particulate hydrous silicic acid having a water content of 4 to 8% by weight, an apparent specific gravity of 0.1 to 0.3, and a particle size of 20 mμ or less is attached to the wax-coated particulate hygroscopic fertilizer substance. It is a characteristic method for preventing solidification of a particulate hygroscopic fertilizer substance.

The method for producing a particulate hygroscopic fertilizer substance such as large-sized urea treated in the method of the present invention is not particularly limited,
For example, a method in which molten urea is granulated in a granulation tower
50-114380), granules obtained by spraying molten urea onto a small lump of urea and prill urea in a fluidized state (JP-A-56-7)
6236) Or granulated with a plate granulator, usually,
A large urea having a particle diameter of 2 to 3 mm is used.

The wax used in the method of the present invention may be a petroleum-based paraffin wax, a microcrystalline wax, or an oxidized wax produced by subjecting a petroleum-based wax to an oxidation process using a catalyst, and has a melting point of 40%.
In the range of -60 ° C, preferably in the range of 40-55 ° C.

The fine particle hydrous silicic acid used in the method of the present invention is produced by a wet method and has a water content of 4 to 9% by weight, an apparent specific gravity of 0.1 to 0.3 (g / ml), a particle diameter of 25 mμ or less,
It is desirable to use amorphous spherical particles having a particle size of 3 to 20 mμ. The purity of silicic acid does not need to be particularly limited.
~ 88 wt% is preferred.

Such fine particle hydrous silicic acid is attached to large-sized urea uniformly coated with wax, and imparts an anti-caking effect while maintaining moisture resistance without damaging the wax coating.

In the method of the present invention, the wax coating on the particulate hygroscopic fertilizer material is not particularly limited, for example, by a method of spraying molten wax at a particle temperature of 40 to 65 ° C., preferably 45 to 60 ° C. on, for example, large urea. Done. The amount of wax added is 0.05 to 0.5% by weight, preferably
0.1 to 0.3% by weight, usually 3 to 8 minutes after spraying,
Preferably, it is rolled for 3 to 5 minutes to uniformly coat the particle surfaces.

The addition method may be either a continuous type or a batch type, as long as a sufficient rolling effect can be obtained as a device, and a rotary mixing drum, a plate type rolling device, a one-man mixer or the like can be used.

The adhesion treatment of the particulate hydrous silicic acid in the method of the present invention is performed on the wax-coated large-sized urea.
Usually, if the wax coating treatment as described above is carried out and then cooled, it can be uniformly adhered to the surface of the wax-coated large-sized urea without impairing the moisture-proof property. Before cooling, since the wax coating is soft, fine particles of hydrous silicic acid penetrate into the wax. As a result, not only a complete moisture-proof effect cannot be obtained, but also an anti-caking effect is insufficient, which is not preferable.

In other words, the particle temperature is 35
It is preferably carried out at a temperature of not higher than ° C. The adhesion treatment method may be a continuous type or a batch type as long as the rolling effect can be sufficiently obtained as an apparatus. A rotary mixing drum, a one-man mixer, or even a cement mixer truck can be used.

The amount added is usually 0.1 to 1% by weight with respect to large-sized urea.
It is preferably 0.2 to 0.5% by weight, and can be appropriately varied depending on the melting point of the wax, the amount of wax, the temperature, and the like. Rolling time is 1 to 7 minutes, preferably 2 to 5
Minutes. Prolonging the treatment time has no effect and adversely affects the wax coating, which is not preferable.

Action and Effect of the Invention As an anti-caking agent, by attaching fine particle hydrous silicic acid to the wax surface of the fertilizer substance, it is possible to prevent the caking without impairing the moisture-proof property.

Therefore, when the method of the present invention is applied to large-sized urea, the surface of the particles can be sufficiently effectively coated as a wax even if the particle temperature is lowered in order to suppress the addition reaction between urea and the wax during the wax coating treatment. Since the product can be selected, it is possible to produce large-sized urea having excellent moisture resistance.

Further, since the large-sized urea produced by the method of the present invention is not slow-released, there is no difference in handling from ordinary urea, and since the fine particle hydrous silicic acid is hydrophilic, the anti-floating effect can be obtained.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to Examples.

Example 1 A paraffin wax (MP5) which was heated and melted into large-sized urea having a temperature of 60 ° C. by a batch method using a rotary mixing drum having a capacity of 5.
(5 ° C.) was sprayed at 0.2% by weight, tumbled for 5 minutes, coated, and allowed to cool to room temperature. A predetermined amount of the above wax-coated large-sized urea was put into a rotary mixing drum used for wax coating, and fine particles of hydrous silicic acid (trade name: Zeocile # 1000V made by Taki Chemical Co., Ltd., water content 5 wt%, apparent specific gravity 0.15 to 0.19 g / ml, particle diameter 15-20
mμ) (hereinafter abbreviated as S / F) was added to each of 0.1, 0.3, 0.5 and 1% by weight and tumbled for 3 minutes.

With respect to the large-sized urea treated in this way, a moisture absorption rate determination and a solidification test were carried out. For comparison, an example in which S / F is not added is also shown.

In addition, the moisture absorption rate measurement method was to precisely weigh 10 g of a sample on a Petri dish (with a lid), put it in a humidity chamber at a temperature of 30 ° C., RH of 80%, and a wind speed of 2.5 m / S, and measure the weight after 24, 48 and 72 hours. .

On the other hand, in the consolidation test, 350 g of a sample was placed in a cylinder type 10 cmφ SUS container and stored for 2 days at a room temperature of 40 ° C. and a humidity of RH of 40% under a load of 0.55 Kg / cm ² .

The load was removed and the consolidation hardness was measured with a Yamanaka soil hardness meter.

The results are shown in Table-1.

Comparative Example 1 In order to see the effect of addition of fine particle hydrous silicic acid, the same test as in Example 1 was carried out using another siliceous powder (SiO ₂ content 45 to 80 wt%, water content 1% or less).

The results are shown in Table-2.

Example 2 Large-sized urea granulated in the fluidized bed system was made into a product-sized particle size by a sieving machine. This product had a particle temperature of 55 ° C. and was continuously supplied to a rotary mixing drum, sprayed with an oxidizing wax (MP 51 ° C.), tumbled for 5 minutes, and stored in a warehouse.

The product treated in this way is continuously supplied to a rotating drum, and at the same time, 0.3% of fine particle hydrous silicic acid (trade name Carplex # 80 Shionogi Pharmaceutical Co., Ltd.) (3-2) and the above-mentioned Zeocile # 1000V are used.
Addition of 0.3% (3-3) was performed for 2 minutes by tumbling and adhesion.

1 for each of these processed products 30 to 35 by filling container bags and stacking each in two layers
Stored at ℃ for 2 weeks, 1 month, 3 months to investigate the discharge status of the lower container bag. The results are shown in Table-3.

For comparison, an example (3-1) of the S / F-free product is also shown.

From the results in Table 3, the S / F-added product could be discharged without handling even after storage for 3 months, and the moisture absorption rate did not change at all during storage.

Claims (1)

[Claims] 1. A wax-coated particulate hygroscopic fertilizer material, further having a water content of 4 to 9% by weight and an apparent specific gravity of 0.
A method for preventing solidification of a particulate hygroscopic fertilizer substance, which comprises attaching spherical fine particles of hydrous silicic acid having a particle size of 1 to 0.3 and a particle size of 25 mμ or less.