EA039898B1 - Fertilizer pellets with micronized sulphur - Google Patents

Abstract

Fertilizer pellets may be formed by compressing or compacting a primary fertilizer powder mixed with micronized sulphur.

Description

Plants require essential nutrients such as carbon, hydrogen, oxygen, nitrogen, phosphorus, and potassium, as well as minor nutrients and trace elements, to grow vigorously. Calcium, sulfur and magnesium are minor nutrients and are usually needed in smaller amounts than the major nutrients. Trace elements are needed in very small amounts, and they include zinc, manganese, iron, copper, molybdenum, boron, chlorine, cobalt, and sodium.

Potassium available in the soil is usually supplemented with potash (also known as potassium hydrochloride (KA) or potassium chloride). Soil-available phosphorus is often supplemented with a solid phosphate fertilizer, usually monoammonium phosphate (MAP), diammonium phosphate (DAP) or calcium dihydrogen phosphate or monocalcium phosphate (Ca(H2PO ₄ )2), known as triple superphosphate (TSP). Available nitrogen can be supplemented with urea. These fertilizers with the main nutrients are commonly known as NPK fertilizers.

Methods for the preparation of MAP and DAP are conventional and usually involve reacting phosphoric acid (H ₃ PO ₄ ) with ammonia (NH3) in an exothermic reaction.

H ₃ RO ₄ + ΝΗ ₃ => (ΝΗ ₄ ) Η ₂ ΡΟ ₄ (MAF)

H ₃ RO ₄ + 2 NH ₃ => (NH ₄ ) ₂ HPO ₄ (DAF)

Such reactions can take place in a preneutralizer or in a cruciform tubular reactor (CTR). The preneutralizer is a stirred reactor in which ammonium phosphate slurry is produced. The cruciform tube reactor is a tube-shaped reactor in which ammonium phosphate is produced by reacting ammonia and phosphoric acid.

In each case, MAF or DAF (or their combination) can be obtained, depending on the ratio of the reagents - ammonia and phosphoric acid. The suspension of ammonium phosphate obtained in the preliminary neutralizer is fed into the granulator. The ammonium phosphate obtained in the KTP is sprayed in the granulator because the ammonium phosphate obtained in the KTP is in a melt state.

Calcium dihydrogen phosphate or monocalcium phosphate (Ca(H2PO4)2), known as triple superphosphate (TSP), can be obtained by reacting phosphoric acid with phosphate rock.

In general, solid fertilizer particles are obtained by granulating, pelletizing or pressing. The granulator is a device for obtaining finished fertilizer granules. Commonly used granulators are well known in the art and include spray-drying granulators, drum granulators, paddle mixers (horizontal drum paddles) or trough granulators. Preferably, the mixture is pressurized and distributed on a rotating bed of material in a drum granulator. Water and/or steam may be supplied to the granulator to control the temperature of the granulation process. The granules are then dried and screened, returning the oversized and oversized granules (so-called off-spec fines) back to the granulator. Too large particles can be crushed or crushed before being fed back to the granulator. Too small and crushed large particles returned to the cycle perform an important function, providing seed particles to initiate the formation of granules in the granulator.

In contrast, pelletizing is a process by which a powdered material is formed into granules by pressing. In the first stage, the fertilizer material may be processed, for example, in a crusher, hammer mill, or similar device, to produce a powder containing relatively uniform fine particles, typically less than about 0.70 mm in size, or fine enough to pass through a standard 25 mesh sieve. American Particle Scale. At this stage, minor and trace elements in powder form can be added as additives and mixed with said powder. The powdered material can then be mixed and wetted with a small amount of water in preparation for pelletizing. After the mixture has been brought to the desired moisture content, the mixture may be subjected to pelletization using a granulation device such as a mill or a press in which compression is used to obtain granules. Suitable pelletizing presses are well known in the art and may include screw type pelletizing extrusion presses.

Pressing is similar to pelleting in that a pressing force is used to produce granules, but differs from pelleting in that it uses a much higher pressing force to stick solid particles together. To obtain a good quality pressed product, raw materials are needed in powder form with suitable particle size. Since the raw materials are usually only available in coarse form, they must be passed through a grinder to obtain a fine powder.

- 1 039898

However, any grinding or pressing process to process sulfur inherently carries a high risk of fire or explosion. Elemental sulfur is flammable and can potentially ignite or explode in the manufacturing process. The grinding medium always generates heat, which can ignite the combustible raw material, causing an explosion.

The essence of the invention

In one aspect, the invention includes a process for making a finished fertilizer comprising the steps of making a powdered fertilizer suitable for pelleting or pressing, adding micronized sulfur in the required amount to form a mixture, agitating the mixture, and obtaining cohesive granules by pelletizing the mixture. In one embodiment, the mixture is compressed at high pressure, which may be greater than about 5 kpsi. inch (34.5 MPa). The resulting compressed granules are very dense (greater than about 1.5 g/cm ³ ) and have high crush strength (greater than about 20 pounds or 9 kg).

In another aspect, the present invention includes a process for producing a fertilizer granule comprising the steps

a) obtaining powdered fertilizer and adding micronized sulfur particles and/or trace elements to powdered fertilizer;

b) adjusting the moisture content of the fertilizer powder mixture to about 5% to about 25% water (w/w); and

c) shaping the powdered fertilizer granules using the compression molding process.

In one embodiment, the fertilizer material contains a phosphate fertilizer from a source of phosphorus. The phosphorus source may contain phosphoric acid and the phosphate fertilizer may contain MAP and/or DAP.

Particles that are too fine or too large after the pelletizing step can be recycled to the return stream, wherein the return stream has a recycle rate of less than 300% on a dry matter basis and preferably a recycle rate of less than about 200%, 100%, 50%, or 30% on a dry matter basis. for dry matter.

In another aspect, the present invention may include a compression granule containing phosphate fertilizer particles. The granule may optionally contain micronized particles of sulfur and/or other nutrient or trace element.

In one embodiment, the granule has a crush strength of greater than about 1.4 kg, an abrasion resistance (ATR) of greater than about 95%, and/or a dispersibility of greater than about 70% when passed through a 12 mesh American sieve. 300 from immersion in water.

In another aspect, the invention may include a compacted or compacted granular fertilizer comprising a water-soluble NPK fertilizer and micronized sulfur particles having a crush strength of greater than about 1.4 kg and a dispersibility greater than 70% when passed through a 12 mesh American sieve for particle measurement in 300 seconds of immersion in water obtained without the use of a binder, wetting agent, dispersant or disintegrant.

Detailed description

In this context, the terms used have the following meanings. All other terms and expressions used in this description have the standard meanings understood by those skilled in the art. The standard meaning can be found with reference to technical dictionaries such as Hawley, Condensed Chemical Dictionary 14th edition, RJ. Lewis, John Wiley & Sons, New York, NY, 2001.

This invention relates to granular fertilizers containing basic fertilizer and micronized elemental sulfur obtained by pelletizing or pressing. The base fertilizer may contain a water soluble NPK fertilizer such as urea, potash, phosphate, or combinations thereof. As used herein, a granule is a cohesive or adhesive mass of smaller particles that is compressed, and a compressed granule is a granule that is compressed at a pressure greater than about 5,000 psi. inch (34.5 MPa).

In one embodiment, this invention may relate to compressed granular fertilizers containing any water-soluble NPK fertilizer and micronized sulfur. The fertilizer material is pulverized prior to the addition of sulfur to form a compressible powder.

The methods of the present invention are relatively flexible in that the granular fertilizer can easily be supplemented prior to pelletizing or pressing.

The phosphate fertilizer added to the granules of the present invention may be prepared by any known method and may contain triple superphosphate (TSP), monoammonium phosphate (MAP) and/or diammonium phosphate (DAP). In general, a phosphate fertilizer can be obtained by using phosphoric acid and a cation source such as calcium from fluorapatite or hydroxyapatite (phosphate ore), ammonium, sodium, or potassium to form a fertilizer compound. In one embodiment, the implementation of MAF or DAF is obtained through the interaction between phosphoric acid and ammonia. For example, where applicable, the methods described in US Pat. No. 7,497,891, the entire contents of which are incorporated herein by reference, are particularly suitable. Typically, MAP and/or DAP is produced by a combination of a pre-neutralization reaction and a reaction in a cruciform tubular reactor. The preparation of ammonium phosphate is started in a preneutralizer and the reaction is carried out to completion in a cross-shaped tubular reactor. The pre-neutralizer can be loaded with phosphoric acid and ammonia. The reaction then proceeds in a cross-shaped tubular reactor (CTR), which is also loaded with phosphoric acid and ammonia. In one embodiment, micronutrients can be incorporated into the fertilizer by initially dissolving the micronutrients in acid prior to being fed into the preneutralizer or KTP. Different ratios of products may be produced in the KTP and preneutralizer, or they may be completely produced in one reactor but not in the other.

The preneutralizer is a stirred reactor in which ammonium phosphate slurry is produced. MAP or DAP (or a combination thereof) can be obtained in the preneutralizer, depending on the ratio of ammonia and phosphoric acid. The contact time in the preneutralizer may be from 5 to 55 minutes, more specifically from 15 to 45 minutes, and even more specifically from 25 to 35 minutes.

KTR is a tube-shaped reactor in which ammonium phosphate is produced by reacting ammonia and phosphoric acid. As in the preneutralizer, MAP or DAP (or a combination of both) can be produced in KTR. The heat dissipated at the outlet of the CTE can be about 600,000 Btu/hr/in (27.25 kW/cm) because the reaction between ammonia and phosphoric acid is exothermic. The high temperature in the KTP promotes the forward reaction at a high rate.

The MAP or DAP produced in the pre-neutralizer contains a liquid slurry, while the MAP or DAP produced in the KTR is a melt. In either or both cases, the MAP or DAP may be dried, cooled and solidified in a cooling tower or spray dryer in which the MAP or DAP particles are produced. Average particle size and morphology are highly dependent on drying, cooling and solidification conditions. The resulting fertilizer material is then usually granulated in a granulator. However, in various embodiments of the present invention, the resulting material is not granulated, but rolled. Granulation is a process by which a particle is formed by cumulatively attaching small particles to each other or to a seed particle by adhesion to form a granule. The resulting granules are usually amorphous and can have a wide range of sizes and morphologies.

In contrast, pelletizing is a process by which a powdered material is formed into granules by pressing or compacting. In various embodiments of this invention, as a first step, the fertilizer material may be processed, for example, in a crusher, hammer mill or similar device, to obtain a powder containing relatively uniform fine particles, preferably with an average diameter of less than about 1 mm (passing through a 18 mesh), more preferably less than about 0.84 mm (fine enough to pass through a 20 mesh sieve), and even more preferably less than about 0.70 mm (fine enough to pass through a 25 mesh American Particle Scale) or less.

Before or during mixing of the powder, micronized elemental sulfur may be added to the mixture. In one embodiment, micronized sulfur particles may be added, such as those described in the same applicant's US Pat. No. 8,679,446. The micronized sulfur particles preferably have an average particle diameter of less than 100 microns, or more preferably 30 microns. Most preferably, the micronized sulfur particles have an average diameter of 10 microns or less. The micronized sulfur product preferably contains sufficient moisture to minimize dusting and to minimize flammability, for example about 2 to 10% by weight. For example, a moisture content of from about 5% to about 7% (by weight) provides safety for transportation and further processing, since such a product is not dusty or flammable. It is undesirable to add elemental sulfur at the crushing (powdering) stage, since sulfur dust is an irritant, an explosion hazard at handling devices, and is easily segregated. In one embodiment, the implementation of sulfur can be added to a concentration of from about 5 to 95% or more, preferably from about 10% to about 30% on a dry basis.

At this stage, other necessary ingredients can be added to the powder and mixed with it as additives. The additives are preferably also in the form of a powder or in a form which rapidly breaks down or solubilizes upon wetting. Additives may include other major, minor or trace elements (such as, for example, zinc sulfate, zinc oxide,

- 3 039898 manganese, manganese oxide, copper sulfate, sodium molybdate and any other compositions of trace elements); fertilizer compounds (such as, for example, potassium chloride, calcium sulfate, magnesium sulfate, etc.); binders (such as, for example, starch, lignosulfonates, molasses, etc.); carbon (such as, for example, activated carbon, carbon matrix, etc.); dispersants, such as, for example, surfactants, etc.) or other materials (such as, for example, humic acid, fulvic acid, etc.), which can be added at this stage in the required concentration. Such additives may be added in amounts necessary to achieve any desired additive concentration. For example, if you need 1% (by weight) zinc as a trace element, you can add 27.8 kg of zinc sulfate monohydrate (ZnSO ₄ -H ₂ O) per metric ton or 14.7 kg of zinc oxide (ZnO) per metric ton . The additives may be in the form of a powder which rapidly breaks down or solubilizes upon wetting.

In one embodiment, the powdered material may then be mixed and wetted with a small amount of water in preparation for pelletization. Preferably, such material contains from about 5% to about 25% by weight of water, and more preferably from about 7% to about 20% by weight of water. This water content contributes to the cohesive properties of the resulting granule.

After the mixture has been brought to the desired moisture content, the mixture may be subjected to pelletization using a granulation device such as a mill or a press in which compression is used to obtain granules. Suitable pelletizing presses are well known in the art and may include screw type pelletizing extrusion presses. At a moisture content of greater than about 7% (w/w), the powdered material has sufficient cohesion to form granules with sufficient integrity for further transport and use without the use of a binder. If necessary, but not necessarily, a binder may be added.

The granules produced by the granule maker are then screened to remove granule fragments or other material that is too small or too large, and the discarded material is returned to the return stream. The return stream may be returned to the mixer or may be used in another process. In one embodiment, the present inventors have found that such a granule process results in surprisingly low recycle compared to a granulation process, while still producing industrial quality granules. In one embodiment, the recycle ratio may be less than about 300%, or less than about 200%, or less than about 100%. A recycling ratio of 1:1 or 100% means that for every kilogram of produced pellets that meet specification, one kilogram of material is returned to the cycle. In particularly preferred embodiments, the recycle ratio may be less than 200%, 100%, 50%, 40%, or 30%, and may be as low as about 10% to about 15%. This may compare favorably with known granulation processes for the production of MAP or DAP, in which the recycling ratio is on the order of 5:1 or 500%. Such high recirculation ratios necessitate the use of special process return streams and significantly increase the capital cost of an industrial plant.

The granules conforming to the specification may be dried and sieved again, and the finished product conforming to the specification may be cooled and coated as is known in the art.

The granules may have a composition essentially entirely composed of phosphate (such as MAP or DAP (or both)), or may contain other major, minor or trace elements.

The granules of the present invention produced in a granulation press may have an average particle diameter of from about 0.4 mm to about 15 mm. More preferably, the average particle domain size is from about 0.6 mm to about 10 mm. Even more preferably, the average particle domain size is from about 0.8 mm to about 5 mm. The granules obtained by the process of this invention have a uniformity index of 30 to 95, where the uniformity index is calculated as the percentage of the ratio of the number of particles having a size characteristic of 10% of the particles to the number of particles having a size characteristic of 95% of the particles. More preferably, the uniformity index is between 60 and 90.

The granules according to the invention may have any shape determined by the pelletizing process. Examples include spheres, cylinders, ellipses, rods, cones, disks, needles, and irregular shapes. In one embodiment, the granules are approximately cylindrical, and in another embodiment, they are irregularly shaped.

The granules of this invention have a crush strength that can be from about 1.4 kg per granule to about 8 kg (from about 3 pounds to about 18 pounds) per granule or more, which can be achieved without the addition of a binder, although the binder a substance may optionally be added.

The granules according to the present invention may have an abrasion resistance of 95% or more, and more preferably 99% or more. The test itself involves agitation of the particles, typically by tumbling in a drum, vibration or gas jets to simulate a fluidized bed.

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After a certain time, the material is sieved and the sieved material is weighed to measure that portion of the material that has been ground to a size below a certain value (referred to as fine particles). The RCI value of 95% means that after a certain time the granules retain

95% of its weight. The test characteristics define various standards applicable for the purpose in question, such as ASTM, well known to those skilled in the art.

The granules of the present invention are dispersible to form a dispersion of 25% or more, and more preferably 70%, and more preferably 90% or more of a dispersion, when passed through a 12 mesh American particle sieve after 300 seconds of immersion in water. Such dispersibility can be achieved without the addition of a wetting agent, disintegrant or dispersant, although such agents may optionally be added.

In an alternative embodiment, the base fertilizer, such as MAP and/or DAP produced in the reactor, is not granulated, but subjected to separate grinding using, for example, a hammer mill, basket mill or roll crusher. Then the obtained fine-grained powder is mixed with micronized sulfur.

The wet micronized sulfur powder may then be mixed with the powdered MAP and/or DAP using any standard mixer such as a barrel mixer, ribbon mixer or screw mixer. Any additional nutrients or micronutrients can be added at this time. In one embodiment, no binder is required. The blended powder is then compressed using standard compaction equipment such as a double roller compactor to form a granular product. Preferably, pressures greater than about 5000 psi are used for sealing. inch (34.5 MPa), 10 kpsi inch (kilo pounds per square inch) (69 MPa), 20 or 30 kpsi inch (138 or 207 MPa).

In one embodiment, MAP, DAP, or potash having an average particle size of about 100 to 300 microns is particularly suitable for compaction. In one embodiment, an average particle size of 180 microns is preferred.

In one embodiment, the fertilizer material is blended with elemental micronized sulfur in a ratio of about 1% to about 30% powdered sulfur by weight of the final product, and preferably in a ratio of about 15% to about 25%.

The resulting compressed granules preferably have a density greater than about 1.5 g/cm ³ , preferably greater than about 1.60 g/cm ³ , and more preferably greater than about 1.80 g/cm ³ . In some embodiments, a density of about 2.00 g/cm ³ can be achieved.

The compressed experimental pellets may have a crush strength greater than about 20 pounds (9.1 kg), preferably greater than about 30 pounds (13.6 kg), and more preferably greater than about 50 pounds (22.7 kg). In some embodiments, crush strengths greater than 100 pounds (45.4 kg) or even 200 pounds (90.7 kg) can be achieved. The granular product may have a lower crush strength compared to experimental granules, which can be used to determine the compressibility of various formulations.

The finished product is soluble in water and rapidly decomposes in the soil when moistened. Thus, micronized sulfur is rapidly dispersed in the soil and can be oxidized in situ. In one embodiment, since the bulk of the granule is water soluble, no wetting agent or dispersant is required to achieve sufficient dispersion, however, a wetting agent, dispersing agent, and/or disintegrant may optionally be added.

Examples

The following examples are presented only to illustrate specific embodiments of the present invention, and not to limit the claimed invention.

Received two batches of 20 kg of the mixture (in terms of dry matter), containing the following ingredients:

i) 17 kg of MAF, ground in a hammer mill to obtain a fine enough powdered material to pass through a 25 mesh sieve on the American scale for measuring particles;

ii) approximately 3.21 kg of micronized sulfur with an average diameter of less than 10 µm at a moisture content of 7% (3.0 kg of sulfur on a dry matter basis); and iii) water in such an amount that the moisture content of the mixture is up to about 9-10% (on a dry matter basis).

Then mixed and stirred powdered MAF, micronized sulfur and water to obtain a mixture. The resulting mixture was pelletized using a pelletizing press manufactured by Amandus Kahl (Germany) model No. 14-175 and a die with 3 mm holes, at a compression ratio of 4:1 or 3:1.

The following parameters were measured:

moisture content of micronized sulfur (before mixing with MAF);

final moisture content;

the mass of small particles formed (recycle estimate, since the product of too large size was not obtained).

Standard quality control tests were performed after drying for 12 hours at 70° C., including % dispersion on passage through a 12 mesh sieve, American Particle Scale after 300 seconds of water immersion, abrasion resistance (ATS), and crush strength.

results

The consignment Mouthpiece Moisture content in sulfur (%) Moisture content of the mixture (%) Crushing strength (lb/granule) SCI (%) Dispersion after 300 seconds (%) Content of fine particles (kg) BUT 4 5.1 9.4 17.66 (8.0 kg) 99.2 78 5.2 AT AP 6.1 ten 10.72 (4.9 kg) 99.4 90 5.9

The dried ΜΑΦ+S granules were found to be of commercially acceptable quality with high dispersion, high crush strength and good abrasion resistance. The measured recycling rate (fine particles) was from 5.2 to 5.9 kg per 20 kg of powdered material (from 26 to 29.5% in terms of dry matter). The nutrient content of the granules was about 9% nitrogen, 44% P ₂ O ₅ and 15% sulfur.

In the following examples, MAF powder having an average particle size of about 180 microns was mixed with micronized sulfur powder having an average particle size of less than 10 microns and a bulk density of 0.507 g/cm ³ . The mixed powder was then compressed into 10 g experimental granule samples using a double roller compactor at 10, 20, and 30 kpsi. inch (69, 138 and 207 MPa).

At a ratio of 85/15 (ΜΑΦ/S by weight), the resulting experimental pellets had a density greater than 1.69 g/cm ³ and a crush strength of at least 108 pounds (49.0 kg) and more than 220 pounds (99.8 kg) for samples pressed at a higher pressure._____________________

Pressure (kpsi) Sample (g) Granule area (sq. inch) Thickness (inch) Density (g/ ^cm3 ) Crushing strength (lb) Fresh Through 1.5 h at 200°F (93°C) After 24 24 hours at 70°F (21°C) Blend of 85% MAF with 15% sulfur 1A 10 (69 MPa) ten ¹ (6.45 cm2) 0.360 (0.91 cm) 1.69 118 (53.5 kg) 1A 10 (69 MPa) ten ¹ (6.45 cm2) 0.364 (0.92 cm) 1.68 108 (49.0 kg) 1B 20 (138 MPa) ten ¹ (6.45 cm2) 0.337 (0.86 cm) 1.81 >220 (99.8 kg) sample received 5x10 mesh 1B 20 (138 MPa) ten ¹ (6.45 cm2) 0.330 (0.84 cm) 1.85 >220 (99.8 kg) 1C 30 (207 MPa) ten ¹ (6.45 cm2) 0.330 (0.84 cm) 1.85 >220 (99.8 kg) 1C 30 (207 MPa) ten ¹ (6.45 cm2) 0.328 (0.83 cm) 1.86 >220 (99.8 kg)

At a ratio of 75/25 (ΜΑΦ/S by weight), the resulting experimental pellets had a density greater than 1.72 g/cm and a crush strength of at least 62 pounds (28.1 kg) or more.

115 pounds (52.2 kg) for specimens pressed at higher pressure. Pressure (kpsi) Sample (g) Pellet area (sq. inch) Thickness (inch) Density (g/ ^cm3 ) Crushing strength (lb) Fresh Through 1.5 h at 200°F (93°C) After 24 hours at 70°F (21°C) Blend of 75% MAF with 25% sulfur 2A 10 (69 MPa) ten ¹ (6.45 cm2) 0.355 (0.90 cm) 1.72 62 (28.1kg) 2A 10 (69 MPa) ten ¹ (6.45 cm2) 0.352 (0.89 cm) 1.73 64 (29.0 kg) 2B 20 (138 MPa) ten ¹ (6.45 cm2) 0.333 (0.85 cm) 1.83 115 (52.2 kg) 2B 20 (138 MPa) ten ¹ (6.45 cm2) 0.331 (0.84 cm) 1.84 125 (56.7 kg) 2C 30 (207 MPa) ten ¹ (6.45 cm2) 0.328 (0.83 cm) 1.86 128 (58.1 kg) 2C 30 (207 MPa) ten ¹ (6.45 cm2) 0.330 (0.84 cm) 1.85 136 (61.7 kg)

Potash granules having a bulk density of 1.054 g/cm ³ were also mixed with the micronized sulfur described above in a ratio of 85/15. The resulting experimental pellets had a density greater than 1.90 g/cm ³ and a crush strength of at least 23 pounds (10.4 kg) and more than pounds (16.8 kg) for samples compressed at higher pressure.

Pressure (kpsi) Sample (g) Pellet area (sq. inch) Thickness (inch) Density (g/ ^cm3 ) Crushing strength (lb) Fresh After 1.5 hours at 200°F (93°C) Through 24 h at 70°F (21°C) Blend of 85% potash as delivered with 15% sulfur BEHIND 10 (69 MPa) ten ¹ (6.45 cm2) 0.319 (0.81 cm) 1.91 23 (10.4 kg) BEHIND 10 (69 MPa) ten ¹ (6.45 cm2) 0.321 (0.82 cm) 1.90 35 (15.9 kg) SW 20 (138 MPa) ten ¹ (6.45 cm2) 0.308 (0.78 cm) 1.98 55 (25.0 kg) SW 20 (138 MPa) ten ¹ (6.45 cm2) 0.310 (0.79 cm) 1.97 42 (19.1 kg) AP 30 (207 MPa) ten ¹ (6.45 cm2) 0.306 (0.78 cm) 1.99 44 (20.0 kg) AP 30 (207 MPa) ten ¹ (6.45 cm2) 0.306 (0.78 cm) 1.99 37 (16.8 kg)

By crushing and screening the potash through a 70 mesh sieve before mixing and pressing it, the crush strength of the finished granules increased significantly.

Pressure (ksi) Sample (g) Pellet area (sq. inch) Thickness (inch) Density (g/ ^cm3 ) Crushing strength (lb) Fresh After 1.5 hours at 200°F (93°C) Through 24 h at 70°F (21°C) Blend of 85% potash ground to less than 70 mesh with 15% sulfur 5A 10 (69 MPa) ten ¹ (6.45 cm2) 0.322 (0.82 cm) 1.89 70 (31.8 kg) 5A 10 (69 MPa) ten ¹ (6.45 cm2) 0.322 (0.82 cm) 1.89 78 (35.4 kg) 5V 20 (138 MPa) ten ¹ (6.45 cm2) 0.306 (0.78 cm) 1.99 130 (59.0 kg) sample received 5x10 mesh 5V 20 (138 MPa) ten ¹ (6.45 cm2) 0.307 (0.78 cm) 1.99 138 (62.6 kg) 5C 30 (207 MPa) ten ¹ (6.45 cm2) 0.303 (0.77 cm) 2.01 128 (58.1 kg) Blend of 75% potash, ground to less than 70 mesh, with 25% sulfur 6A 10 (69 MPa) ten ¹ (6.45 cm2) 0.321 (0.82 cm) 1.90 56 (25.4 kg) 6A 10 (69 MPa) ten ¹ (6.45 cm2) 0.321 (0.82 cm) 1.90 56 (25.4 kg) 6B 20 (138 MPa) ten ¹ (6.45 cm2) 0.305 (0.77 cm) 2.00 93 (42.2 kg) 6V 20 (138 MPa) ten ¹ (6.45 cm2) 0.306 (0.78 cm) 1.99 83 (37.7 kg) 6C 30 (207 MPa) ten ¹ (6.45 cm2) 0.304 (0.77 cm) 2.01 70 (31.8 kg) 6C 30 (207 MPa) ten ¹ (6.45 cm2) 0.303 (0.77 cm) 2.01 86 (39.0 kg)

Definitions and interpretation

The description of the present invention is provided to demonstrate and describe, and is not intended to be an exhaustive or limiting description of the present invention in the form described. Numerous modifications and variations will be understood by those skilled in the art without deviating from the scope and general idea of the present invention. Embodiments are selected and described to best explain the principles of the invention and practice, and to enable those skilled in the art to understand the invention for various embodiments with various modifications suitable for the particular intended application.

Relevant structures, materials, acts, and equivalents of all means or steps and functions of the elements in the claims appended to this specification include any structures, materials, or acts to perform said function in combination with other explicitly stated elements.

In this description, the mention of one of the implementation options, implementation options, etc. means that the described implementation option may include a specific aspect, feature, structure

- 7 039898 or characteristic, but not every implementation option necessarily includes such an aspect, feature, structure or characteristic. In addition, such expressions may refer, but do not necessarily refer to the same implementation variant mentioned in other parts of the description. In addition, when describing a particular aspect, feature, structure, or characteristic with respect to one embodiment, those skilled in the art may use or associate such aspect, feature, structure, or characteristic with other embodiments, whether explicitly described or no. In other words, any element or feature can be combined with any other element or feature in various implementations, except in cases of obvious or natural incompatibility of such two elements or cases of their special exclusion.

Additionally, it should be noted that the claims may be drafted to exclude any optional element. Therefore, such a statement serves as a preliminary basis for the use of exclusive terminology such as only, singular, etc., in relation to the enumeration of claimed elements or for the application of a negative limitation. The terms preferred, preferred, prefer, optional, may, and like terms are used to refer to an element, condition, or step mentioned as an optional feature of the invention.

The singular form includes the plural form, unless the context clearly indicates otherwise. The term and/or means any of the specified elements, any combination of elements, or all elements to which the term refers.

Those skilled in the art should understand that all numerical values, including values expressing amounts of reactants or ingredients, properties such as molecular weight, reaction conditions, etc., are approximations and should be construed as being optionally modified in all instances by the term near. Such values may vary depending on the desired properties to be obtained by experts in the art using the ideas and descriptions presented in this document. It should also be understood that such values inherently contain variability necessarily resulting from the standard deviations associated with the respective experimental measurements.

The term about can refer to a deviation of ±5, ±10, ±20, or ±25% of the specified value. For example, about 50 percent in some implementations may mean options from 45 to 55%. For integer ranges, the term about may include values one or two units greater than and/or less than the specified integer at each end of the range. Unless specifically noted otherwise, in this context, the term about includes values and ranges close to the specified ranges, which are equivalent in terms of the functionality of the composition or implementation.

Those skilled in the art, for any and all purposes, especially with regard to providing a written description, will appreciate that all ranges described herein also encompass any and all possible subranges and combinations of subranges, as well as all individual values forming said range, in particular integer values. The range represented (eg, weight percent or carbon groups) includes every single value, integer, decimal value, or unit within the range. Any listed range can be easily recognized as a range providing sufficient description, with the possibility of subdividing the same range into at least equal halves, thirds, quarters, fifths, tenths, or other fractional parts. As a non-limiting example, each range described herein can be easily divided into a lower third, a middle third, and an upper third.

It will also be appreciated by those skilled in the art that expressions such as up to at least more than, less than, more, or more, etc., include the amount indicated, and that such terms refer to ranges that may then be divided into subranges as described above. In the same way, all ratios specified in this document also include all intermediate ratios included in the broader ratio. Accordingly, the specific meanings listed for radicals, substituents, and ranges are for illustrative purposes only; they do not exclude other defined meanings or other meanings within the defined ranges for the indicated radicals and substituents.

It will also be understood by those skilled in the art that if the elements are grouped in a standard way, for example, into Markush groups, then this invention includes not only the entire group described as a whole, but also each element of the group individually, as well as all possible subgroups of the main group. In addition, this invention covers for all purposes not only the main group, but the main group in the absence of one or more elements of the group. Thus, the present invention provides for the explicit exclusion of any one or more elements of the described group. Accordingly, with respect to any of the described categories or embodiments, conditions may be used whereby any one or more of the described elements, particles, or embodiments may be excluded from such categories or embodiments, for example, when used in an explicit negative limitation.

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CLAIM

Claims (17)

CLAIM 1. A method for producing granular fertilizer, which includes the steps of grinding a water-soluble NPK fertilizer to obtain a fertilizer powder that has an average particle size of 100 to 300 microns, adding micronized sulfur in an amount of 1 to 30% on a dry matter basis to the powder to obtain a mixture of fertilizer powder and micronized sulfur, mixing the mixture, and pressing the mixture into solid granules using a pressure of more than 69 MPa to form granules with a crushing strength of more than 22.7 kg per granule. 2. Method according to claim 1, characterized in that a pressure of more than 138 MPa is used in the pressing step. 3. Granular fertilizer obtained by the method as claimed in claim 1, which contains a mixture of water-soluble NPK fertilizer powder having an average particle size of from 100 to 300 microns, and micronized elemental sulfur in an amount of from 1 to 30% in terms of dry matter, when that the granule has a density of more than 1.50 g/cm ³ and a crush strength of more than 22.7 kg. 4. Granular fertilizer according to claim 3, characterized in that it contains from 10 to 30% micronized sulfur in terms of dry matter. 5. Granular fertilizer according to claim 3 or 4, characterized in that the density is more than 1.60 g/cm ³ . 6. Granular fertilizer according to claim 5, characterized in that the density is more than 1.80 g/cm ³ . 7. Granular fertilizer according to claim 6, characterized in that the density is more than 2.00 g/cm ³ . 8. Granular fertilizer according to claim 3, characterized in that its crushing strength is more than 45.4 kg per granule. 9. Granular fertilizer according to claim 8, characterized in that its crushing strength is more than 90.7 kg per granule. 10. A method for producing granular fertilizer, comprising the following steps: (a) obtaining a fertilizer powder containing NPK fertilizer and having a particle size of less than 1 mm, adding micronized sulfur particles in an amount of 10 to 30% on a dry basis to the fertilizer powder to obtain a mixture of fertilizer powder and micronized sulfur particles; (b) adjusting the moisture content of the mixture to a range of 5 to 25% water (w/w); (c) forming pellets from the mixture using a compression molding process; and (d) screening the granules having an average particle size in the range of less than about 0.4 mm and greater than about 15 mm, after the step of forming the granules into granules of the desired size, less than the desired size, and granules over the desired size, and returning the granules , the size of which differs from the desired size into the recycle stream, and the recycle stream has a recirculation ratio of less than 300% in terms of dry matter. 11. Method according to claim 10, characterized in that the NPK fertilizer contains MAP and/or DAP. 12. The method of claim 10, further comprising the step of adding trace elements to the fertilizer powder prior to the step of forming the granule. 13. Process according to claim 10, characterized in that the recycle stream has a recycle ratio of less than 200% on a dry matter basis. 14. The method according to claim 13, characterized in that the recirculation ratio is less than 100%. 15. The method according to claim 14, characterized in that the recycling rate is less than 50%. 16. The method according to claim 15, characterized in that the recycling rate is less than 40%. 17. The method according to claim 16, characterized in that the recycling rate is less than 30%.