KR19990077527A - A coating process for fertilizers - Google Patents

Abstract

A method for producing a coated granular fertilizer containing elemental sulfur in a coating using calcium oxide, calcium hydroxide or calcium sulfate as a coating additive is disclosed. The method comprises the steps of: (a) adding raw fertilizer to a mixing and coating apparatus, (b) adding an aqueous solution or water containing soluble phytonutrients, and (c) a mixture of sulfur or calcium oxide, potassium hydroxide and sulfide Adding a coating additive selected from the group consisting of calcium. Therefore, it is possible to produce a fertilizer coated with a coating containing elemental sulfur (S), which is a granule containing raw phosphate or sulphate. The raw material fertilizer is, for example, ammonium phosphate (MAP), diammonium phosphate (DAP), single superphosphate (SSP), double superphosphate (DSP), triple superphosphate (TSP), sulfide of ammonium (SoA), It may be a sulfide of caustic potassium (SoP) or Langbeinite (K-Mag), preferably porous.

Description

Coating method of fertilizer {A COATING PROCESS FOR FERTILIZERS}

The present invention relates to a coating method that is readily available and can be finely sprayed onto the surface of granular fertilizers, in particular finely formed on the granular monoammonium phosphate.

Up to about 40 years ago, inorganic plant nutrient sulfur, although it played a very important role in the metabolic function of plants, was not of interest to seedling scholars or fertilizer manufacturers.

This is mainly due to the fact that (a) Sulfur deficiency symptoms are similar to nitrogen deficiency symptoms and are often described as nitrogen deficiency. (b) Low resolution fertilizers often contain relatively large amounts of these nutrients. (c) Prior to the 1960s, sulfur deficiency only occurred in certain regions of the world. (d) Due to severe pollution, a significant amount of atmospheric sulfur is supplied to the soil. And (e) most pesticides comprise sulfur (ie, lime-sulfur, Bordeaux liquid, etc.).

Mineral nutrients Deficiency of sulfur is well known to hinder plant growth. As mentioned above, the symptoms of yellow deficiency are similar to those seen in nitrogen deficient plants, that is, yellowing uniformly, fragile and thinning stems, and inhibiting growth.

In addition to these sulfur deficiencies, LB Fenn and the Texas Agricultural Laboratories and El Paso Association found that the addition of sulfur to strong calcareous soils reduced soil dehydration and calcium, manganese and phosphorus contents. LB Fenn, RM Taylor and CA Pety Jr, (1987) J Plant Nutrition, 10,2263-2281. Inconsistencies were found during Fenn's and especially Flocker's research, which indicated that plants grown in non-calcine soils absorbed more calcium than plants grown in very strong calcareous soils [WJ Flocker and WH Fuller, (1956), "Availability of calcium in calcareous soils", Soil Sci Coc Amer Proc, 20,387-391]. With respect to this finding, it should be remembered that calcium carbonate is only slightly soluble and the solubility of various calcium carbonate products is as follows. That is, the solubility product of calcium carbonate (CaCO ₃₎ constant is 2.8 × 10 ^-9, and the solubility product of aragonite (Aragonite) constant is 6.0 × 10 ^-9, and the solubility product of calcite (Calcite) constant is 4.5 × 10 ^{- 9} is. The use of this type of calcium in the soil is due to the fact that the roots of plants do not produce sufficient carbon dioxide from respiration to produce an appropriate amount of calcium ions. In addition, Fenn was able to demonstrate that the presence of calcium, magnesium and potassium ions in the soil not only promoted the uptake of nitrogen by the plant, but also reduced the reduction of nitrogen in the calcareous soil.

In view of the above studies, many researchers in the field of fertilizer technology have concentrated their efforts on the mixing of elemental sulfur into granular high-degradable fertilizers. In relation to this technique, the following two types of coating methods are disclosed in several earlier patents.

(a) spraying granular fertilizers, in particular sulfur dissolved in the surface of the urea;

In contrast to most phytonutrients concealed primarily by physicochemical methods in the soil's root zone, nitrogen is extremely mobile and easily filtered out of the root zone. The purpose of the coating method is to reduce the loss of nutrients by spraying molten sulfur, melted wax or bitumen on the fertilizer granules by spraying. Sulfur or other molten materials solidify to prevent nutrients from being released from the granules and to form an almost impermeable shell on the surface of the granules. Representative examples of such coating methods are described in U.S. Pat. No. 3,672,613, issued April 27, 1971 to PS Fleming, U.S. Pat. No. 4023,319, issued June 28, 1977 to L Smith, March 28, 1978, to WR Ali. US Patent No. 4041264, and the like. Solidified sulfur with a relatively low surface area will only be slowly oxidized by thio-bacilli in the soil and will be available for years to come.

(b) Preparation of a strongly adherent coating containing sulfur which is readily available in finely separated states;

The purpose of the coating method is to generate a matrix comprising finely separated sulfur which is readily oxidized by thio-bacilli in the soil on the surface of the granules and thus readily available to plants. Representative examples of the coating technique are as follows.

In Australian Patent No. 601099 K H Walter presents a coating of granular fertilizers using elemental sulfur by adding ammonium sulfate as a coating additive. It has been found that the method reacts very well with single, double and triple superphosphates. The coating formed on this form of fertilizer is very strongly attached and has a high erosion resistance. However, ammonium phosphate does not react well to the coating method by itself.

In International Patent No. PCT / AU91 / 00459, Lefroy et al. Used the use of water-soluble adhesives such as PVA, sodium lignosulphonate or calcium lignosulphonate to produce coated fertilizer granules. Presented. Unfortunately, the coating by this method further requires a drying step to form a coating with strong adhesion. This is not only expensive, but also has the problem of dust explosion.

In Australian Patent No. 52601/93 (669403) JD Johnston has a glass of thermal energy that mixes diluted inorganic acids, sulfur and / or at least one micronutrient, and acid neutralizers and fertilizer granules whereby water is removed as water vapor. A method of producing a coated granular fertilizer material is produced by causing precipitation of a reactant of at least one acid with a neutralizing agent that binds to the surface components of the granules in the form of a coating that is simultaneously attached.

Unfortunately, the heat of reaction generated is too low to evaporate the amount of water produced in the system by using diluted inorganic acids. This means that an additional drying step is required, and furthermore, by using a non-nutrient neutralizing agent for the neutralization of the acid, the result contains significantly lower nutrients.

In Australian patent 45576/96 Hi-Fert Pty Ltd proposes the use of magnesium oxide (MgO) and ammonium phosphate (NH ₄ ) 2 HPO ₄ for the sulfur-coating of urea. The coating formed by this method does not adhere very strongly to urea granules.

Australian patent 77314/98 has shown that sulfur coated on the surface of di-ammonium phosphate (DAP) with magnesium oxide as a coating additive forms a coating that is strongly adherent to erosion resistance. This forms more reactive magnesium hydroxide (Mg (OH) ₂ ), where magnesium oxide reacts immediately with water and, in turn, with DAP and forms hydrated ammonium struvite. The struvite ((NH ₄ ) MgPO ₄ .6H ₂ O) will encapsulate the granules and contain finely separated sulfur.

Unfortunately, neither ammonium nor potassium can form on the surface of ammonium phosphate (MAP), which usually has a pH of about 4.5. Since both struvites will only form when the pH is above about 7.5, one must look for other compounds that can retain the sulfur and form a strongly attached matrix. In studying higher adhesion sulfur coatings, we found that other magnesiums, such as hanyite (Mg ₃ (NH ₄ ) ₂ (HPO ₄ ) ₄ .8H ₂ O) and schertelite, An ammonium phosphate mixture was found and these two compounds were found to be useless as long as the MAP coating is concerned.

In research for a better coating system, we find that calcium oxide (CaO), calcium hydroxide (Ca (OH) ₂ ) and calcium sulfate (CaSO ₄ ) are excellent coating additives, as well as sulfur coating of MAP, as well as di-phosphate Ammonium (DAP), single superphosphate (SSP), double superphosphate (DSP), triple superphosphate (DSP), dense ammonia sulphate (SoA), potassium sulphate (SoP), also known as many potassium deposits worldwide It has also been found to be an excellent additive for granular fertilizers such as langvenite (K-Mag), an inorganic (K ₂ SO ₄ .2MgSO ₄ ).

Accordingly, the present invention provides a coated granular fertilizer containing elemental sulfur in a coating, characterized by using calcium oxide (CaO), calcium hydroxide (Ca (OH) ₂ ) or calcium sulfate (CaSO ₄ ) as a coating additive. To a method or system. Throughout the description and claims, it should be noted that calcium sulfate (suitably) includes hydrates such as hemihydrates (Plasters of flies) and dihydrates.

The present invention provides a method for producing a fertilizer coated with a coating containing elemental sulfur (S), the raw fertilizer is a granule containing phosphate or sulfate, comprising the steps of: (a) injecting the raw fertilizer into a mixing and coating apparatus, (b) adding an aqueous solution or water containing soluble plant nutrients, and (c) adding a mixture of sulfur or a coating additive selected from the group consisting of calcium oxide, potassium hydroxide and calcium sulfide. To provide. As used in the description and claims of the present invention, the terms "granular" and "granular" are included within the scope of the indented output.

The raw material fertilizer is, for example, ammonium phosphate (MAP), diammonium phosphate (DAP), single superphosphate (SSP), double superphosphate (DSP), triple superphosphate (TSP), sulfide of ammonium (SoA), It may be a sulfide of caustic potassium (SoP) or Langbeinite (K-Mag), preferably porous.

The addition of calcium oxide, calcium hydroxide or calcium sulphate to sulfur containing fertilizers such as SoA, SoP and K-Mag has resulted in the formation of calcium sulfate dihydrate (CaSO ₄ · 2H ₂ O) and some complex double salts on the surface of the fertilizer as follows: Will form.

Ca (OH) ₂ + 2H ₂ O + K ₂ SO ₄ → CaSO ₄ 2H ₂ O + 2KOH

_{Ca (OH) 2 + 2K 2} SO 4 + H 2 O → CaK 2 (SO 4) 2 · H 2 O + 2KOH

_{2Ca (OH) 2 +4 (NH} 4) 2 SO 4 → 2Ca (NH 4) 2 (SO 4) 2 · H 2 O + 4NH 3 + 2H 2 O

In the case of non-phosphate fertilizers, the reaction between the fertilizer and the additive, which is calcium oxide, calcium hydroxide or calcium sulfate (e.g., calcined gypsum: CaSO ₄ 1 / 2H ₂ O) as a feed of calcium, More complex than that indicated in 2 and 3. The inventors expect that the following compounds may be formed during the coating of the fertilizer comprising sulfur.

Gippsum:

Calcium sulfate dihydrate (CaSO4 · 2H2O) is widely distributed in nature and usually exists in the vapor phase.

SYNGENITE:

CaK ₂ (SO ₄ ) ₂ H ₂ O exists in nature in the vapor phase, in particular in the caustic potassium precipitate, and forms in the mixed fertilizer. Form isomers with koktaites.

KOKTAITE:

Ca (NH ₄ ) ₂ (SO ₄ ) ₂ H ₂ O is generally present in Gibbs Island and in anhydrous gypsum precipitate in the vapor phase.

POLYHALITE:

Ca ₂ K ₂ Mg (SO ₄ ) ₄ .2H ₂ O is generally present naturally in potassium salt precipitates.

We have found that calcium oxide, calcium hydroxide, calcium sulfate are good coating additives used to coat sulfur on granular MAP. In contrast to magnesium, the divalent charge of calcium ions does not react with ammonium phosphate or alkali phosphate to form a highly hydrated mixed phosphate salt that is stable at ambient temperature. Double salts of alkali phosphates with divalent metal ions have been known for more than 100 years [H Rose, (1849) annual physik, 77,292].

Calcium ammonium phosphate heptahydrate (CaNH ₄ PO ₄ · 7H ₂ O) is stable only at low temperatures and decomposes to calcium phosphate and ammonia at ambient temperature [AW Frazier, JR Lehr and JP Smith, (1964) J Agr Food Chem , 12, 198-201.

After considering all aspects, the inventors have concluded that the following compounds will be best formed during the coating of sulfur-containing MAP using calcium oxide or calcium hydroxide as the coating additive. The type of compound to be formed will be a function of pH, temperature, and liquid concentration.

Monocalcium and Calcium Phosphate:

_{2 (NH 4) H 2 PO} 4 + CaO + 2H 2 O → Ca (H 2 PO 4) 2 · H 2 O + 2NH 4 OH

NH ₄ H ₂ PO ₄ + Ca (OH) ₂ + H ₂ O → CaHPO ₄ 2H ₂ O + NH ₄ OH

Hydroxyapatite: Ca ₁₀ (PO ₄ ) ₆ (OH) ₂

Despite the fact that the pH of the surface of the MAP granules is generally too low to form hydroxyapatite, the inventors believe that a high concentration of calcium hydroxide on the surface will lead to the formation of the microcrystalline compound. The inventors are based on the above description that the resulting coating dries significantly faster than any other coating process during the coating process. I think this is due to the precipitated phosphate, which has a small particle size to act like a colloid. That means it can absorb significant amounts of water without sticking and sticking. This phenomenon is due to the widespread use of precipitated calcium phosphate as an inhibitor against aggregation of hygroscopic and tacky materials. This compound, one of the most stable calcium phosphates from a thermodynamic perspective, will be formed as follows.

6 NH ₄ H ₂ PO ₄ +10 Ca (OH) ₂ → Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ +6 NH ₃ +18 H ₂ O

Calcium ammonium _{phosphate: CaNH 4 PO 4 · H 2} O

The compound is found in fertilizers combined with ammonia and is a reactant of calcareous minerals with ammonium phosphate.

_{NH 4 H 2 PO 4 + Ca} (OH) 2 → CaNH 4 PO 4 · H 2 O + H 2 O

Dicalcium monoammonium heptahydrogen phosphate: Ca ₂ NH ₄ H ₇ (PO ₄ ) ₄ 2H ₂ O

The acid salt is formed as follows.

4 [NH ₄ H ₂ PO ₄ ] + 2CaO → Ca ₂ NH ₄ H ₇ (PO ₄ ) · 2H ₂ O + 3NH ₃

Mono calcium mono diammonium hydrogen _{phosphate: Ca (NH 4) 2 (} HPO 4) 2 · H 2 O

The compound is present in soil as well as fertilizers that are stable and mixed in air.

_{2NH 4 H 2 PO 4 + Ca} (OH) 2 → Ca (NH 4) 2 (HPO 4) 2 · H 2 O + H 2 O

Considering these reactions involving phosphate, all phosphate high-fertilizer fertilizers are prepared from commercially containing acids, so that any impurities (sulfates, silicon fluorides, depending on the type of phosphate rock used in the preparation) , Fluoride, aluminum, iron, magnesium, and organic materials can be detected). Since many of these impurities react with the coating additive (Ca), the reaction takes place much more complicated than that shown in Schemes 1-9 above.

The inventors have used CaO, Ca (OH) ₂ or CaSO ₄ to maintain a finely separated elemental sulfur of at least 20% w / w agriculturally available to form a strongly adherent coating throughout the experiment. It has been found that a coating method is possible. However, this coating method works best when the granular fertilizer is porous and is not produced by vibration of large crystals.

Coating operations for the incorporation of elementalization into granular fertilizers are usually carried out optimally using equipment used in agglomerative granulation processes. Fertilizer granules are preferably "porous" in the sense that each granule does not consist of only one large crystal, but can be prepared by conventional wet aggregate granulation processes or dry consolidation processes. Processes of this type always produce granules with a porous surface that is easy to coat rather than the soft surface of large crystals.

The most commonly used agglomerate granulators are rolling drum granulators and inclined pan or disc granulators. There are many other flocculating devices that can be used for coating fertilizers, such as the SackettStar Granulator, Falling Curtain granulator, etc., but these devices are considered to be variations of conventional drum granulators. do.

While excellent coating results can be obtained using a pan granulator with a fan diameter of 2 or less for pan rim height, we believe that drum granulators with annular rings are superior to any other granulation or coating apparatus. Here it is.

The present inventors used the granulation apparatus which satisfy | fills the following design specification in production calculation work.

Drum Design Variables:

Ratio of drum length to drum diameter = 2.4 / 1

Height to radius of annular ring = 0.3 / 1 or more

Drum tilt angle = 1.5 ° or less

Nominal% ratio of bed volume to total drum volume = 30% or more

Coating time = more than 15 minutes

Drum rotation speed = 40% or more and 60% or less of Ncs

Actual length of drum = 3.0 m

Actual rotational speed of drum = 48.6% of Ncs or 13.0 rpm

Ncs is the critical speed, defined as the centrifugal force acting on the granules at a distance of "r" from the center of the drum and the rotational speed with the gravity acting on the granules when the granules are at the top of the rotation. This means that the following equation (1):

g = rω ²

Here, g is a gravitational acceleration according to gravity (= 9.81 m / sec ² ), 2r is the diameter of the drum in meters, and ω is the angular velocity per second in radians. Thus, the threshold speed is as follows:

Critical Speed Ncs = 42.317 / 2r rpm

The inventors have found that a coating drum that meets the above specification forms a bed that falls like a cascade of granules, which has ideal mixing properties for the coating operation, and because of its depth, By continuously supplying the granules to a vibrating bed that is significantly larger than the shallow bed, the coating formed on the surface of the granules is densified and pushed into the pores of the granules. This compacting mechanical force is very important in order to keep the consumption of coated water to a minimum and to ensure that the coating applied to the granules adheres strongly to the soft and finished granules.

Although coating in shallow beds is possible, the quality of the finished coating is very poor compared to coatings formed in deep beds. This is partly due to the fact that the number of coatings required for shallow beds is significantly higher than for deep beds, which is due to the fact that the pores formed between the individual crystals in the reactions that occur during the coating operation fall down like granules. It will increase significantly compared to the void of the bed.

The crystals of the deep bed drum coating apparatus are densified to the extent that they are held together at a fairly strong adhesion, rather than much weaker adhesion resulting from liquid filled pores as in the case of coating in a shallow bed.

Experimental Examples

Hereinafter, the present invention will be described in detail with reference to experimental examples, but the following experimental examples do not limit or limit the present invention.

Note on raw materials:

Fertilizer:

Fertilizers meet the following conditions:

(a) Fertilizers are prepared by the size-enlarging method and are produced with porous granular particles having a total volume of pores that varies within a range of 25% to 40%.

(b) The size range of the fertilizer is 2 mm or more and 6 mm or less (the granular size range is not an important factor).

Sulfur:

Since the main purpose of this sulfur coating process is to supply nutrient sulfur to plants and to allow plants to absorb sulfur only in the form of ions, elemental sulfur must be oxidized primarily in the soil and dissolved in water. It must be changed. This change from elemental form to water soluble form can occur as a result of the auto-oxidation of elemental sulfur in the presence of oxygen and moisture in the soil or in the presence of sulfur-bacteria in the soil, the sulfur-bacteria being oxidized. The energy released during the reaction is used for their metabolism.

Whatever the actual process of change, the sulfur coated on the surface of the fertilizer must be separated in a fine state or, in other words, have a large surface area in order to be easily oxidized.

The size of sulfur used was as follows:

Sulfur Size:

0.5 mm or less = 99.5% w / w 0.25 mm or less = 97% w / w

0.15 mm or less = 92% w / w 0.075 mm or less = 78% w / w

Hydrated Lime:

Hydrated lime used in this test example is Australian standard No. The conditions according to AS 1672 were met.

In the present pilot plant, which can coat 10 to 15 tph of fertilizer as well as the present pilot plant batch coating apparatus capable of coating about 10 kg of fertilizer per plant, before the pulverized sulfur containing hydrated lime is added. It is very important to add about 70% of the total water.

Sulfur and additives should never be added first. Compared with fertilizers, the fact that sulfur and additives have a very large surface area means that (a) they are severely separated on the vibrating bed and (b) they absorb more water than fertilizers due to the large specific surface area, and calcium hydroxide In addition, wet sulfur coalesces with wet particles of less than 2 mm of fertilizer and forms small granules. The result is a product of coarse coated fertilizer granules and small granules consisting of a sulfur additive and a fine fertilizer.

The spray used to entrain the water should be fine enough to adequately distribute the coating water to the fertilizer granules falling like a waterfall, but to the extent that the inside of the coating drum becomes wet and spray drift occurs. It should not be fine.

In the following examples, all percentages are by weight and the number of coatings is expressed as% w / w of the total solids content.

Experimental Example 1

In this experiment in a pilot plant, mono-ammonium phosphate (MAP) was coated with varying amounts of coating additives and sulfur.

Table 1 below summarizes the work performed in the pilot plant.

Coating time = 15 minutes Exam number Ammonium Phosphate (MAP) (% w / w) Calcium hydroxide (Ca (OH) ₂ ) (% w / w) Sulfur (S) (% w / w) Water (H ₂ O) (% w / w) 1.1 88.3 1.0 10.7 3.2 1.2 87.3 2.0 10.7 4.8 1.3 78.0 2.0 20.0 4.5

Evaluation of the coating output showed that the coating formed by the present method has good erosion resistance and is superior to coatings by other coating methods.

Experimental Example 2

In the following experiment, the coated fertilizer was Langbeinite (K-Mag). These experiments (and the experiments of Experimental Examples 3 and 4) were performed again in a compact pilot batch coating apparatus.

Exam number Langenite (K-Mag) (% w / w) Calcium hydroxide (Ca (OH) ₂ ) (% w / w) Sulfur (S) (% w / w) Water (H ₂ O) (% w / w) 2.1 88.0 1.0 11.0 2.8 2.2 87.0 2.0 11.0 3.2 2.3 78.0 2.0 20.0 4.0

As mentioned again, the coated output was excellent.

Experimental Example 3

In the experiments below, the coated fertilizer was a sulfate of ammonium (SoA).

Exam number Sulphide of Ammonium (SoP) (% w / w) Calcium hydroxide (Ca (OH) ₂ ) (% w / w) Sulfur (S) (% w / w) Water (H ₂ O) (% w / w) 3.1 88.0 1.0 11.0 4.1 3.2 87.0 2.0 11.0 4.2 3.3 78.0 2.0 20.0 4.6

The coating adhered strongly to the surface of the granules.

Experimental Example 4

In the following experiments, the coated fertilizer was sulfate of Potash (SoP).

Exam number Sodium sulfide (SoP) (% w / w) Calcium hydroxide (Ca (OH) ₂ ) (% w / w) Sulfur (S) (% w / w) Water (H ₂ O) (% w / w) 4.1 88.0 1.0 11.0 4.0 4.2 87.0 2.0 11.0 4.8 4.3 78.0 2.0 20.0 4.8

The coated output is believed to be good as described above.

Experimental Example 5

In the following tests, the coated fertilizer was single superphosphate (SSP).

Granular single superphosphates (SSP) vary in particle size distribution and chemical properties depending on the source. Three different sources were used in this experiment in which all products and products of all yielding properties were within the following specifications.

Particles on the order of 1 to 5 mm in size from 80 to 100% w / w and generally analyzed as follows:

Phosphorus (P) (total amount): 8.8 to 9.2% w / w

Phosphorus (effective amount): 8.6 to 8.9% w / w

Sulfur as sulfate: 11-13.2% w / w

The addition of calcium oxide (CaO) or calcium hydroxide (Ca (OH) ₂ ) to a single superphosphate (SSP) was calculated using monocalcium phosphate; Ca (H ₂₎ for the fertilizer granules themselves according to Schemes 10-12 below. PO ₄ ) ₂ · H ₂ O) and / or calcium diphosphate (CaHPO ₄ · H ₂ O).

2H ₃ PO ₄ (phosphoric acid) + Ca (OH) ₂ (calcium _{hydroxide) → Ca (H 2 PO 4} ) 2 · H 2 O ( one calcium phosphate) + H ₂ O

With salt-based calcium monophosphates already present in a single superphosphate:

Ca (OH) ₂ (calcium _{hydroxide) + H 2 O + Ca (} H 2 PO 4) 2 · H 2 O ( one calcium _{phosphate) → 2CaHPO 4 · 2H 2 O} ( calcium phosphate)

_{3Ca (H 2 PO 4) 2} · H 2 O ( one calcium phosphate) + 7Ca (OH) ₂ (calcium _{hydroxide) → Ca 10 (PO 4)} 6 (OH) 2 ( hydroxyapatite; hyrdoxyapatite) + H ₂ O

Sulfur (S) is deeply contained in the strongly adherent coating of calcium monophosphate and / or calcium diphosphate and / or hydroxyapatite.

Table 5 below summarizes the results of the work performed in the pilot plant. Coating time was 15 minutes.

Exam number Single superphosphate (SSP) (% w / w) Calcium hydroxide (Ca (OH) ₂ ) (% w / w) Sulfur (S) (% w / w) Water (H ₂ O) (% w / w) 5.1 89 1.0 10 8.0 5.2 79 1.0 20 10.0 5.3 78 2.0 20 12.0

The tests showed coating results with levels of dust removal superior to any other coating methods.

Experimental Example 6

In production operations using continuous coating drums as described above, ammonium phosphate (MAP) was coated under the following conditions:

Feed speed:

Ammonium Phosphate (MAP) = 8.9 t / h

Sulfur (S) = 1.1 t / h

Water = 230 l / h = 2.3% w / w

The sulfur used in this production operation contained 10% w / w of hydrated lime.

The output produced according to the present invention has undergone extensive testing not only in rice fields but also in production plants. The results of this test showed that the coating had good erosion resistance.

As described above, although described with reference to the preferred embodiments of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the present invention described in the claims below. And can be changed.

Claims (10)

In the manufacturing method of the fertilizer coated with a coating containing elemental sulfur (S) containing the raw material fertilizer granular phosphate or sulfate, (a) injecting the raw fertilizer into a mixing and coating apparatus; (b) adding an aqueous solution or water containing soluble plant nutrients; And (c) adding a mixture of sulfur or a coating additive selected from the group consisting of calcium oxide, potassium hydroxide and calcium sulfide. According to claim 1, wherein the raw fertilizer is ammonium phosphate (MAP), diammonium phosphate (DAP), single superphosphate (SSP), double superphosphate (DSP), triple superphosphate (TSP), sulfide of ammonium (SoA) , A method of producing a fertilizer, characterized in that the sodium sulfide (SoP) or langbeinite (Langbeinite; K-Mag). The method for producing a fertilizer according to claim 1 or 2, wherein the raw fertilizer is porous. The method for producing a fertilizer according to any one of claims 1 to 3, wherein the coating additive is calcium oxide. The method of producing a fertilizer according to any one of claims 1 to 3, wherein the coating additive is calcium hydroxide. The method of claim 1, wherein the coating additive is calcium sulphate. The method for producing a fertilizer according to any one of claims 1 to 6, wherein the sulfur has a finely divided form. 8. The method of claim 1, wherein the water is sprayed onto the granules of the raw fertilizer in the step of adding an aqueous solution or water containing the soluble phytonutrients. 9. . The method for producing a fertilizer according to any one of claims 1 to 8, which is substantially as described in Experimental Examples 1 to 6. A coated granular fertilizer prepared according to the method of any one of claims 1 to 9.