JP7683192B2 - Method for producing granular ammonium sulfate composition - Google Patents

Description

The present invention relates to a granular ammonium sulfate composition, a mixed fertilizer composition, and a method for producing the granular ammonium sulfate composition.

Ammonium sulfate, a nitrogen fertilizer, is obtained industrially by contacting coke oven waste gas with sulfuric acid, or by crystallizing the aqueous ammonium sulfate solution obtained by adding ammonia to caprolactam sulfate during the caprolactam production process. The physical properties required for ammonium sulfate as a fertilizer are "no hindrance to mechanical fertilization," "most particles fall within the particle size range of 2-4 mm," "average crushing strength of 2 kgf or more for particles with particle size of 2.0-2.8 mm," "moisture content of 1.0% or less," "angle of repose of 40° or less," and "no adverse effect on the physicochemical quality of the product, such as caking" (Non-Patent Document 1).

Powdered and fine-granular ammonium sulfate products have small particles that tend to fly around, so they are prone to generating dust and clogging flow paths when spread mechanically, making them unsuitable for the essential requirement of a fertilizer, which is that it should not interfere with mechanical fertilization. The fact that they generate little dust when spread and are less likely to clog flow paths is important when fertilizing large areas of farmland, where mechanical spreading is the norm.

In order to overcome these issues, it is being considered to granulate powdered and finely granulated ammonium sulfate into powdered nitrogen fertilizer with a particle size of approximately 2 to 4 mm, which will result in a fertilizer with high crushing strength and good fluidity due to the large particle size.

For example, in order to provide a method for granulating ammonium sulfate that has physical properties suitable for fertilizer, such as less burrs, high crushing strength, high nitrogen concentration, and resistance to caking, a method for granulating nitrogen fertilizer by controlling the pocket size, granulation pressure, and burr thickness when compressing and granulating the nitrogen fertilizer (Patent Document 1) has been proposed.

In addition, when granular ammonium sulfate is produced, if the granulated ammonium sulfate produced during long-term storage when handled as fertilizer solidifies, this leads to poor workability during mechanical spraying. For this reason, methods to suppress solidification have been considered. For example, when granulating granular fertilizer, a method is known in which an anti-caking agent such as wax or a surfactant is added to part of the raw material, and then the remaining raw material is mixed and compressed for granulation (Patent Document 2); a method is known in which the granular fertilizer is coated by mixing a solution containing trehalose or other sugars as a solute, thereby suppressing the absorption and release of moisture and preventing solidification (Patent Document 3); a method is known in which talc with a specified particle size and purity is added and mixed (Patent Document 4); a method is known in which dicyandiamide is added (Patent Document 5); a method is known in which fine crystalline ammonium sulfate is used as the raw material, and when the angle 2θ between the direction of the incident X-ray and the direction of the detector is 72.3° when the raw crystalline ammonium sulfate is subjected to two-dimensional X-ray diffraction, the degree of orientation is 0.995 or more (Patent Document 6); and a method is known in which the fertilizer contains 20 to 50% by weight of magnesium fertilizer components (Patent Document 7).

The quality philosophy of Kumiai Fertilizer (National Federation of Agricultural Cooperative Associations)

JP 2013-177287 A JP 2013-245147 A JP 2013-163625 A JP 2017-186200 A Japanese Unexamined Patent Publication No. 56-22697 JP 2017-132659 A JP 2019-172561 A

As mentioned above, various granular nitrogen fertilizers and their manufacturing methods have been proposed, and measures have been taken to prevent caking, which is a problem during long-term storage of granular ammonium sulfate, but sufficient effects have not been obtained. Patent Document 1 describes that, with granular products, the particle size is large, so the crushing strength is high, and the specific surface area is low, so the moisture content is low and caking is unlikely to occur. However, if the crushing strength is high and the specific surface area is low, the moisture content is not necessarily low, and if the moisture content is high, caking will occur even if the particle size is large. Patent Document 2 describes adding an anti-caking agent such as wax or a surfactant to a portion of the raw ammonium sulfate, mixing it with the remaining ammonium sulfate, and compressing and granulating it to prevent caking by making the surface distribution of the anti-caking agent uneven. However, this method requires a mixing process of the mixture and ammonium sulfate in addition to the mixing process of the anti-caking agent and the raw material. In Patent Document 3, granular nitrogen fertilizer is coated with a solution containing trehalose or other sugars as solutes to prevent caking by suppressing the absorption and release of moisture. However, when an anti-caking agent is added, costs are required for the process of mixing with a solvent for addition and the drying process of evaporating the solvent. In Patent Document 4, talc with a particle size of 10 μm or less and a purity of 90% or more is added and mixed as an anti-caking agent, but selecting or purchasing talc of the described quality is more difficult and costly than purchasing regular talc. In addition, talc usually contains crystalline silica, which is a carcinogenic substance, and its use requires the selection of a talc production area and costs for dust control. Patent Document 5 states that caking can be suppressed by adding dicyandiamide, but no data is provided, making it impossible to quantitatively grasp the caking suppression effect, and the mechanism of caking suppression has not been clarified.

Patent Document 6 describes that caking can be prevented by using highly crystalline, finely crystalline ammonium sulfate with oriented crystals as the raw material, and that in order to obtain highly crystalline ammonium sulfate crystals, the pressure during crystallization must be maintained at 10.1 kPa ABS or higher. However, in general, with continuous crystallization, the crystal particle size and properties fluctuate, making it difficult to maintain operating conditions using crystallinity as an indicator. Patent Document 7 describes that the inclusion of 20-50% by weight of magnesium fertilizer components increases the particle hardness and makes caking less likely to occur, but the amount of magnesium fertilizer is so high that the concentration of ammoniacal nitrogen, a fertilizer component of ammonium sulfate, decreases, and the fertilizer effect of ammonium sulfate cannot be exerted.

As a result of extensive research to solve the above problems, the present invention provides
In order to achieve the above object, the present invention employs the following configuration.
1. A method for producing a granular ammonium sulfate composition, the method comprising the following two steps, the method comprising the steps of:
1) A process in which magnesium sulfate, which forms a hydrate, is mixed with fine crystalline ammonium sulfate and granulated to form granules.
2) A step of regulating the size and shape of the granular ammonium sulfate composition obtained in 1) .
2. A method for producing a granular ammonium sulfate composition, comprising the following three steps, the method comprising the steps of:
1) A process for granulating fine crystalline ammonium sulfate into granules
2) A process for regulating the size and shape of the granular ammonium sulfate obtained in 1).
3) A step of coating the shape-controlled granular ammonium sulfate obtained in 2) with magnesium sulfate, which forms a hydrate .
3. A method for producing a granular ammonium sulfate composition according to 1 or 2 , wherein the ammonium nitrogen content of the granular ammonium sulfate composition is 20.5% or more.
4. The method for producing a granular ammonium sulfate composition according to any one of 1 to 3 , wherein the caking strength of the granular ammonium sulfate composition is 2.0 kg/ ^cm2 or less.
5. A method for producing a granular ammonium sulfate composition according to any one of 1 to 4 , wherein the solidification rate of the granular ammonium sulfate composition is 90% or less.
6. A method for producing a granular ammonium sulfate composition according to any one of 1 to 5 , wherein the granular ammonium sulfate composition has a particle hardness of 2.0 to 5.0 kgf.
7. A method for producing a granular ammonium sulfate composition according to any one of 1 to 6 , characterized in that granulation is performed by compression molding.
8. A method for producing a granular ammonium sulfate composition according to claim 7 , characterized in that the raw material is compressed by a briquetting method using a pair of rollers to produce a granulated product.

According to the present invention, by preparing a granular ammonium sulfate composition that contains a very small amount of metal sulfate as an anti-caking agent, it is possible to obtain a granular ammonium sulfate composition that has high ammonia nitrogen, high particle hardness, and is resistant to caking during storage.

The present invention will be described in detail below with reference to the embodiments.

The caking of granular ammonium sulfate occurs when free moisture in the raw material moves to the surface, or when moisture in the air is absorbed, causing the surface to dissolve and recrystallize, turning the liquid bridges into solid bridges that bond the particles together. Metal sulfates have a polar molecular structure, and many of them form hydrates. Therefore, it is thought that hydration inhibits the movement of free moisture and inhibits the formation of bridges between the particles. This has the effect of preventing caking, and also exerts a binder effect by retaining moisture within the particles, which also has the effect of increasing the particle hardness. In addition, metal components such as magnesium and calcium are important components that create the "chlorophyll" in leaves, which is necessary for plant photosynthesis, and metal sulfates such as magnesium sulfate and zinc sulfate are sold as fertilizers themselves, and they work to enhance their effectiveness as fertilizers.

The granular ammonium sulfate composition of the present invention has been found to have a significant anti-caking effect while maintaining a high ammoniacal nitrogen content, high particle hardness, and a fertilizer effect due to the metal sulfate, by adding a very small amount of a metal sulfate that forms a hydrate, such as magnesium sulfate or zinc sulfate, as an anti-caking agent to the raw material.

In other words, in the present invention, by coating or mixing very small amounts of metal sulfate components that form hydrates, such as magnesium sulfate or zinc sulfate, with ammonium sulfate and granulating the mixture, it is possible to produce a granular ammonium sulfate composition that suppresses caking during storage while maintaining a high concentration of ammoniacal nitrogen, which is a fertilizer component of ammonium sulfate, and that is less likely to powder due to its high granular hardness, making it easier to handle and spray mechanically.Furthermore, by including metal sulfates such as magnesium sulfate or zinc sulfate, it is possible to produce a granular ammonium sulfate composition that contains additional fertilizer components necessary for plant growth.

<Granular ammonium sulfate composition>
The moisture content of the granular ammonium sulfate composition of the present invention is preferably 0.5% or less from the viewpoint of preventing the granular ammonium sulfate composition from caking together during long-term storage. It is more preferably 0.3% or less, and even more preferably 0.2% or less, and is most preferably 0% when the moisture is completely dried, since no caking will occur. The moisture content of the granular ammonium sulfate composition is a value measured by the heat loss method according to the official fertilizer analysis method.

The ammoniacal nitrogen content of the granular ammonium sulfate composition is preferably 20.5% or more, and more preferably 21.0% or more, in terms of its fertilizer effect as a nitrogen source per unit weight.

The particle size of the granular ammonium sulfate composition is preferably 2.0 to 4.0 mm to ensure the reach of the fertilizer when applied mechanically. It is more preferably 2.5 to 3.5 mm.

The granular ammonium sulfate composition is preferably round in shape so that when applied mechanically, it will not adhere to the leaves of crops and will fall to the soil. If the granular ammonium sulfate composition is not round, for example, if it is flat-shaped, it will adhere to the leaves and not fall off, resulting in poor nutrient supply, which is undesirable. The particle size of the granular ammonium sulfate composition is measured by sieving.

The granular ammonium sulfate composition preferably has a granular hardness in the range of 2.0 to 5.0 kgf. If the granular hardness is less than 2.0 kgf, the granular ammonium sulfate composition is likely to be powdered during production, and the production yield tends to decrease. Powdering also tends to occur during storage of the granular ammonium sulfate composition, which can cause the granular ammonium sulfate composition to solidify. On the other hand, if the granular hardness exceeds 5.0 kgf, the granular ammonium sulfate composition tends to be poorly disintegrated in the soil, and the fertilizer effect tends to decrease. A more preferable range is 2.5 to 4.5 kgf. The granular hardness of the granular ammonium sulfate composition is measured using a Kiya hardness tester for 20 granules, and the average value is taken as the granular hardness.

In order to facilitate the handling of the granular ammonium sulfate composition, the caking strength is preferably 2.0 kg/ cm2 or ^less . The caking strength is a value measured by pressing the needle into the top surface of the fertilizer using a Yamanaka soil hardness tester. The caking rate is preferably 90% or less. If the caking strength is 2.0 kg/ cm2 or ^less , it is usually pseudo-caking, and the caking easily breaks down, so there is no problem in fertilization. However, if the caking rate exceeds 90%, the fluidity becomes poor, and mechanical fertilization may not be possible, which is not preferable. The caking rate is the ratio of the weight of the caking portion of the granular ammonium sulfate composition after one month of loading with an 80 kg weight for 150 g of the granular ammonium sulfate composition, and is expressed by the following formula.
Consolidation rate = (Consolidated portion weight (g) after loading for one month) /150×100

<Anti-caking material>
The anti-caking agent in the present invention is not particularly limited as long as it is a metal sulfate that forms a hydrate, but potassium sulfate, magnesium sulfate, calcium sulfate, copper sulfate, zinc sulfate, manganese sulfate, cobalt sulfate, and the like, which are used as fertilizer components, are desirable because they can be expected to be effective as a fertilizer.

The anti-caking agent concentration in the granular ammonium sulfate composition of the present invention is preferably 0.05 to 0.5% by weight of metal sulfate that forms a hydrate per 100 parts by weight of the granular ammonium sulfate composition. If it is less than 0.05% by weight, the anti-caking effect is low, the effect of increasing the particle hardness is also low, and the effect of the metal sulfate as a fertilizer component is also low. If it exceeds 0.5% by weight, the ammoniacal nitrogen concentration of the granular ammonium sulfate composition is low, and the fertilizer effect when used as an ammonium sulfate fertilizer is reduced, so the more preferred concentration is 0.1 to 0.3% by weight.

<Method of producing granular ammonium sulfate composition>
In the method for producing the granular ammonium sulfate composition, when the raw materials, fine crystalline ammonium sulfate and anti-caking agent, are mixed, they are mixed in a mixer. There is no particular limitation on the type of mixer as long as they can be mixed uniformly, and a container-rotating mixer such as a horizontal cylinder type, V type, or double cone type, or a container-fixed mixer such as a ribbon type, screw type, or paddle type, can be used, but a paddle type mixer is preferably used because it allows continuous processing.

The granulation method for the granulated ammonium sulfate composition is preferably compression granulation, and the compression granulation device may be any of the tablet type, plate type, or briquette type. However, the tablet type has low production efficiency and makes it difficult to mass-produce the granulated ammonium sulfate composition, and the plate type makes it difficult to produce spherical granulated fertilizer with few burrs, so the briquette type is preferred. For example, the Briquette (registered trademark) BSS type (manufactured by Shinto Kogyo Co., Ltd.) can be used as a compression granulation device for the briquette type.

There is no particular restriction on the method for supplying the fine crystalline ammonium sulfate mixture, which is a mixture of the raw fine crystalline ammonium sulfate and the anti-caking agent, to the compression granulation device. For example, the fine crystalline ammonium sulfate can be stored in a hopper and supplied directly to the granulation device from a transport conveyor attached to the hopper, or it can be supplied to the granulation device from the hopper transport conveyor via a belt conveyor, bucket conveyor, etc.

The granulation pressure refers to the value (linear pressure) obtained by dividing the total load applied to the raw fine crystalline ammonium sulfate mixture by the effective width, and the effective width refers to the major axis of the compressor side of the part where the load is applied to the raw fine crystalline ammonium sulfate mixture. For example, in the tablet method, the effective width is the major axis of the tablet part, and in the briquette method using rollers, the effective width is the length of the part where the raw fine crystalline ammonium sulfate mixture is compressed by the rollers. The granulation pressure is preferably in the range of 0.6 to 30.0 kN/cm, more preferably 3.0 to 20.0 kN/cm, and even more preferably 5.0 to 15.0 kN/cm. If the granulation pressure is lower than the above, the granulation of the fine crystalline ammonium sulfate mixture itself does not occur due to insufficient pressure. If the granulation pressure is higher than the above, the compression granulator is subjected to a load greater than necessary, significantly reducing the life of the equipment.

The burr thickness of a compression granulator refers to the short diameter of the fine crystalline ammonium sulfate mixture at the part where the fine crystalline ammonium sulfate mixture is subjected to a load. For example, in the case of a tablet method, the burr thickness is the short diameter of the tablet part, and in the case of a briquette method using rollers, the burr thickness is the shortest length of the distance (clearance) between the rolls. The burr thickness is preferably in the range of 1.00 to 2.50 mm, and more preferably in the range of 1.20 to 2.00 mm. If the burr thickness is lower than the above, both the crushing strength and yield of the granular ammonium sulfate composition tend to decrease. If the burr thickness is higher than the above, the shape of the granular ammonium sulfate composition becomes unsuitable for fertilizer spreading, and when the granulated granular ammonium sulfate composition is crushed to a uniform particle size, for example, with a vibrating sieve using crushing balls, it is not preferable because it causes the sieve to become clogged.

The granular ammonium sulfate composition granulated by the compression granulator can be crushed, sized, and classified to obtain a granular ammonium sulfate composition in a shape suitable for use as a fertilizer.

In order to obtain a granular ammonium sulfate composition with a uniform particle size, it is preferable to use a crusher to crush the granular ammonium sulfate composition after compression granulation. There are no particular limitations on the type of crusher, and for example, various crushers such as jaw crushers and roll crushers, various mills such as roller mills and cutting mills, and vibrating sieves with added crushing media are preferably used. It is also possible to use a combination of these crushers.

In order to obtain a granular ammonium sulfate composition that is spherical and has few burrs, it is preferable to use a sizer to size the composition. There are no particular limitations on the type of sizer, and for example, high-speed rolling, oscillator, crushing, centrifugal rotation, etc. are preferably used, and it is more preferable to size the granular ammonium sulfate composition using a Marmerizer (registered trademark: manufactured by Dalton), which is a high-speed rolling type spherical sizer.

The processing time of the sieving machine is preferably within the range of 0.2 to 5.0 minutes, and more preferably within the range of 0.3 to 3.0 minutes. If the processing time of the sieving machine is shorter than the above, burr removal from the granular ammonium sulfate composition will be insufficient. If the processing time of the sieving machine is longer than the above, the amount of parts other than the burrs that are cut off will increase, and the yield of the granular ammonium sulfate composition will decrease. Furthermore, since the time required for the sieving process will increase, the yield of the granular ammonium sulfate composition per unit time will also decrease.

The rotation speed of the sieving machine is preferably in the range of 50 to 2000 rpm, and more preferably in the range of 100 to 1500 rpm. If the rotation speed of the sieving machine is lower than the above range, burr removal from the granular ammonium sulfate composition will be insufficient, and the time required for the sieving process will increase, resulting in a decrease in the yield of granular ammonium sulfate composition per unit time. If the rotation speed of the sieving machine is higher than the above range, problems such as increased noise and reduced equipment life will occur.

In order to obtain a granular ammonium sulfate composition having a particle size of a specified size or more, it is desirable to classify the granular ammonium sulfate composition using a classifier. There are no particular restrictions on the type of classifier as long as it is capable of dry classification, but it is preferable to use a vibrating sieve. There are no particular restrictions on the size of the sieve openings as long as the specified particle size can be obtained, but openings of 1.8 to 2.2 mm and 3.8 to 4.2 mm are preferable, and a classification method in which sieves having these openings are combined to obtain a granular ammonium sulfate composition having a particle size of 2.0 to 4.0 mm is preferable.

In order to obtain a granular ammonium sulfate composition that has little burrs, high crushing strength, a high nitrogen concentration, little dust generation, and is less prone to caking, it is preferable to granulate the fine crystalline ammonium sulfate mixture as the raw material using a compression granulator, crush the granular ammonium sulfate composition after compression granulation using a crusher, size the crushed granular ammonium sulfate composition using a spherical sizer, and classify the size-sized granular ammonium sulfate composition using a classifier.

There are no restrictions on the method of transporting the granular ammonium sulfate composition in each process, but gravity drop, conveyor transport, air blowing, etc. can be used, and a method in which the raw materials are transported to the granulator by conveyor transport, and then transported to the crusher, granulator, and classifier by gravity drop is preferred. For the powder-contacting parts of the equipment, including these transport devices, it is preferable to use a material that is corrosion-resistant to the granular ammonium sulfate composition, and it is preferable to use SUS316L or resin.

The fine crystalline ammonium sulfate mixture, which is the raw material, is granulated using a compression granulator, the granular ammonium sulfate composition after compression granulation is crushed using a crusher, the crushed granular ammonium sulfate composition is sized using a sizer, and the sized granular ammonium sulfate composition is classified using a classifier. The fine powder that falls below the sieve can be recycled and mixed into the raw material and used as a raw material.

When the anti-caking agent is coated rather than mixed, fine crystalline ammonium sulfate is granulated and sized to produce granular ammonium sulfate, and then a metal sulfate that forms a hydrate is coated on the surface of the granular ammonium sulfate as an anti-caking agent to produce a granular ammonium sulfate composition fertilizer. As a method of coating, if the granular ammonium sulfate is granulated and sized and classified with a classifier, it may be added at the outlet of the classifier, or mixed and coated using a mixer, or coated by spraying on a conveyer belt, as long as the coating is uniform.

The amount of anti-caking agent added to the granular ammonium sulfate composition is preferably 0.05 to 0.5% by weight per 100 parts by weight of the granular ammonium sulfate composition, and more preferably 0.1 to 0.2% by weight per 100 parts by weight of the granular ammonium sulfate composition in order to obtain a fertilizer with good granular hardness and good disintegrability without loss due to adhesion to the equipment or influence on the nitrogen content per unit weight.

After the granular ammonium sulfate composition is produced by granulation and sieving, it is also possible to dry the granular ammonium sulfate composition to reduce its moisture content. There are no particular limitations on the type of dryer, and hot air heat receiving dryers such as rotary dryers and fluidized bed dryers, and conductive heat transfer dryers such as agitator dryers and infrared heating dryers can be used. However, rotary dryers are preferably used because of their low introduction cost and the sieving effect caused by rotation during drying. The drying temperature is preferably 60 to 150°C, and more preferably 100 to 130°C. If the drying temperature is lower than the above, the moisture reduction by drying becomes insufficient, and the drying time becomes long, leading to powdering inside the device and a deterioration in productivity. If the drying temperature is higher than the above, the decomposition of the granular ammonium sulfate composition causes a decrease in the ammoniacal nitrogen concentration. The drying time is preferably 5 to 60 minutes, and more preferably 10 to 30 minutes. If the drying time is shorter than the above, the drying effect will be low and moisture reduction will be insufficient, and if the drying time is longer than the above, prolonged heating will cause powdering inside the equipment and reduced productivity.

The examples of the present invention are shown below, but the present invention is not limited to the following examples. Here, the parts in the examples indicate parts by weight. The methods for measuring physical properties, etc. are as follows.

(1) Particle Hardness of Granular Ammonium Sulfate Composition The particle hardness of each of 20 particles of granular ammonium sulfate composition was measured using a Kiya hardness tester, and the average value was calculated.

(2) Ammoniacal nitrogen: Among the methods for measuring ammoniacal nitrogen specified in the Official Fertilizer Analysis Methods, this value is measured by the formaldehyde method, in which ammonium ions are converted into hexathinalenetetramine and the liberated acid is titrated.

(3) Moisture content of granular ammonium sulfate composition The moisture content of the granular ammonium sulfate composition was determined by the weight loss upon drying the granular ammonium sulfate composition at 130°C for 3 hours before drying, and was calculated using the following formula.
Moisture content (%)=(weight of granular ammonium sulfate composition before drying−weight of granular ammonium sulfate composition after drying)/(weight of granular ammonium sulfate composition before heating)×100

(4) Consolidation strength of granular ammonium sulfate composition This is the value measured using a Yamanaka soil hardness tester by pressing the needle vertically into the top surface of the fertilizer.

(5) Caking rate of granular ammonium sulfate composition This is the ratio of the weight of the caking portion of the granular ammonium sulfate composition after loading 150 g of the granular ammonium sulfate composition with a weight of 80 kg for one month, and was calculated by the following formula.
Consolidation rate (%) = (Consolidated portion weight (g) after loading for one month) /150×100

Example 1
0.1 parts by weight of magnesium sulfate monohydrate was added to 99.9 parts by weight of fine crystalline ammonium sulfate, and the mixture was mixed by supplying it to a Dow Mixer (manufactured by Shin-Nichinan Co., Ltd.). The raw material was supplied to a Briquette (registered trademark) BSS-IH type (manufactured by Shinto Kogyo Co., Ltd.) as a granulator, and granulated with a roll effective width of 185 mm, a roll pressure of 8.3 kN/cm, a burr thickness of 1.70 mm, a pocket size of 3.9 mm x 0.94 mm, and a roller rotation speed of 85 rpm. After crushing with a coarse crusher, the mixture was put into a three-stage crushing sieve machine (manufactured by Kowa Kogyo Co., Ltd.) having sieves with openings of 6.7 mm, 5.2 mm, and 2.2 mm, and crushed with crushing media (200 nylon hard balls in the upper stage and 200 in the lower stage), and the sieved product was collected. The crushed product on the sieve was then put into a Marmerizer (manufactured by Dalton) and subjected to a sieve size adjustment process at a rotation speed of 225 rpm for 15 seconds, after which it was sent to a circular vibrating sieve (manufactured by Dalton) having a sieve with a mesh size of 2 mm, and after classification, the product on the sieve with a mesh size of 2 mm was collected as a granular ammonium sulfate composition. The granular ammonium sulfate composition had an ammoniacal nitrogen content of 21.1%, a moisture content of 0.1%, a particle hardness of 3.2 kgf, a caking rate of 0.0% after one month of caking test, and a caking strength of 0.0 kg/ cm2 . The results are shown in Table ¹ .

Example 2
0.2 parts by weight of magnesium sulfate monohydrate was added to 99.8 parts by weight of fine crystalline ammonium sulfate, and the mixture was fed to a Dow Mixer (manufactured by Shin-Nichinan Co., Ltd.) as a mixer and mixed, and then a granular ammonium sulfate composition was produced in the same manner as in Example 1. The granular ammonium sulfate composition had an ammoniacal nitrogen content of 21.1%, a moisture content of 0.1%, a granule hardness of 3.4 kgf, a caking rate of 0.0% after one month of caking test, and a caking strength ^of 0.0 kg/ cm2 .

(Example 5)
The raw material was 100 parts by weight of fine crystalline ammonium sulfate. The raw material was fed to a granulator, Briquetter (registered trademark) BSS-IH type (manufactured by Shinto Kogyo Co., Ltd.), and granulated with a roll effective width of 185 mm, a roll pressure of 8.3 kN/cm, a burr thickness of 1.70 mm, a pocket size of 3.9 mm x 0.94 mm, and a roller rotation speed of 85 rpm. The granules were then crushed by a coarse crusher, and then fed into a three-stage crusher/sieve machine (manufactured by Kowa Kogyo Co., Ltd.) having sieves with openings of 6.7 mm, 5.2 mm, and 2.2 mm, and crushed with crushing media (200 nylon hard balls in the upper stage and 200 in the lower stage), and the sieved product was collected. The crushed product on the sieve was then put into a Marmerizer (manufactured by Dalton) and subjected to a sieve size adjustment process at a rotation speed of 225 rpm for 15 seconds, after which it was sent to a circular vibrating sieve (manufactured by Dalton) having a sieve with an opening of 2 mm, and after classification, the product on the sieve with an opening of 2 mm was collected as granular ammonium sulfate. In the recovery section of the circular vibrating sieve process, 0.2 parts by weight of magnesium sulfate monohydrate was added to 99.8 parts by weight of granular ammonium sulfate to coat the surface of the granular ammonium sulfate. The ammoniacal nitrogen of this granular ammonium sulfate composition was 21.1%, the moisture content was 0.2%, the particle hardness was 2.6 kgf, the caking rate after one month of caking test was 82%, and the caking strength was 1.6 kg/ ^cm2 .

(Comparative Example 1)
Granular ammonium sulfate was produced in the same manner as in Example 5. No coating treatment of trace components was performed. The ammoniacal nitrogen of this granular ammonium sulfate was 21.2%, the moisture content was 0.2%, the granular hardness was 1.8 kgf, the caking rate after one month of caking test was 99%, ^and the caking strength was 8.5 kg/ cm2 .

(Comparative Example 2)
Granular ammonium sulfate was produced in the same manner as in Example 5, and then 0.2 parts by weight of talc (Asada Flour Milling SW-A) was added to 99.8 parts by weight of the granular ammonium sulfate in a circular vibrating sieve process to coat the surface of the granular ammonium sulfate with talc. The ammonium nitrogen content of this granular ammonium sulfate composition was 21.1%, the moisture content was 0.1%, the particle hardness was 2.0 kgf, and the caking rate after one month of caking test was 98%, and the caking strength was 7.4 kg/ ^cm2 .

(Comparative Example 3)
96 parts by weight of fine crystalline ammonium sulfate and 4 parts by weight of magnesium sulfate monohydrate were fed to a Dow Mixer (manufactured by Shin-Nichinan Co., Ltd.) as a mixer and mixed. The raw material was fed to a Briquette (registered trademark) BSS-IH type (manufactured by Shinto Kogyo Co., Ltd.) as a granulator, and granulated with a roll effective width of 185 mm, a roll pressure of 8.3 kN/cm, a burr thickness of 1.70 mm, a pocket size of 3.9 mm x 0.94 mm, and a roller rotation speed of 85 rpm. After crushing with a coarse crusher, the mixture was fed to a three-stage crushing sieve machine (manufactured by Kowa Kogyo Co., Ltd.) having sieves with openings of 6.7 mm, 5.2 mm, and 2.2 mm, and crushed with crushing media (200 nylon hard balls in the upper stage and 200 in the lower stage), and the sieved product was collected. The crushed product on the sieve was then put into a Marmerizer (manufactured by Dalton) and subjected to a sieve regulating process at a rotation speed of 225 rpm for 15 seconds, after which it was sent to a circular vibrating sieve (manufactured by Dalton) having a sieve with 2 mm openings and classified, after which the product on the sieve with 2 mm openings was collected as a granular ammonium sulfate composition. The granular ammonium sulfate composition had an ammoniacal nitrogen content of 20.4%, a moisture content of 0.2%, a particle hardness of 3.5 kgf, a caking rate of 0.0% after one month of caking test, and a caking strength of ^0.0 kg/ cm2 .

The present invention makes it possible to obtain a granular ammonium sulfate composition using fine crystalline ammonium sulfate as a raw material, which has high grain hardness and low caking tendency during storage while maintaining a high concentration of ammoniacal nitrogen, a fertilizer component, making it easy to handle as a fertilizer and to spread mechanically.

Claims (8)

A method for producing a granular ammonium sulfate composition, the method comprising the following two steps, the method comprising the steps of:
1) A process in which magnesium sulfate, which forms a hydrate, is mixed with fine crystalline ammonium sulfate and granulated to form granules.
2) A step of regulating the size and shape of the granular ammonium sulfate composition obtained in 1) . A method for producing a granular ammonium sulfate composition, the method comprising the following three steps:
1) A process for granulating fine crystalline ammonium sulfate into granules
2) A process for regulating the size and shape of the granular ammonium sulfate obtained in 1).
3) A step of coating the shape-controlled granular ammonium sulfate obtained in 2) with magnesium sulfate, which forms a hydrate . 3. The method for producing a granular ammonium sulfate composition according to claim 1, wherein the granular ammonium sulfate composition contains 20.5% or more of ammoniacal nitrogen. The method for producing a granular ammonium sulfate composition according to any one of claims 1 to 3 , wherein the caking strength of the granular ammonium sulfate composition is 2.0 kg/ ^cm2 or less. The method for producing a granular ammonium sulfate composition according to any one of claims 1 to 4 , wherein the caking rate of the granular ammonium sulfate composition is 90% or less. The method for producing a granular ammonium sulfate composition according to any one of claims 1 to 5 , wherein the granular ammonium sulfate composition has a particle hardness of 2.0 to 5.0 kgf. The method for producing a granular ammonium sulfate composition according to any one of claims 1 to 6 , wherein the granulation is performed by compression molding. 8. The method for producing a granular ammonium sulfate composition according to claim 7 , wherein the raw material is compressed by a briquetting method using a pair of rollers to produce a granulated product.