EA045168B1 - FERTILIZER COMPOSITION WITH SPRAY COATING - Google Patents

Description

Field of invention

The present invention relates to fertilizer compositions and more particularly to fertilizer formed by spray-coated granules.

State of the art

Plants need primary macroelements for intensive growth, as well as secondary macroelements and microelements. Primary macroelements include carbon, hydrogen, oxygen, nitrogen, phosphorus and potassium. Secondary macronutrients include calcium, sulfur and magnesium, and are usually required in smaller quantities than primary macronutrients. Micronutrients are required in very small quantities and include zinc, calcium, magnesium, manganese, iron, copper, molybdenum, selenium, boron, chlorine, cobalt and sodium.

Any fertilizer that contains elemental sulfur is desirable if most of the sulfur is oxidized to plant-available sulfate form during the season of application. However, sulfur oxidizes slowly in soil because it is dependent on microbial colonization and activity. Oxidation rates increase if the sulfur particles are smaller due to the increased surface area available for microbial colonization. Therefore, it is desirable to use micronized sulfur particles.

Macro- and microelements are typically added to the soil using fertilizer in the form of solid particles formed by granulation, pelletizing or pressing. Granulation is typically carried out using granulators well known in the art, including spray dry granulators, drum granulators, paddle mixers (horizontal drum paddle mixers), fluidized beds, briquetting machines or tray granulators. For example, a fertilizer mixture may be fed and distributed onto a rolling bed of material in a drum granulator. Water and/or steam may be supplied to the granulator to control the temperature and humidity of the granulation process. The granules are then dried and screened, and the oversized granules and undersized material (called off-spec fines) are returned back to the granulator. The overgrid material may be shredded or ground first before being fed back to the granulator. The undersized and crushed overgrid material provides seed particles that promote granule formation in the granulator and form a recirculation stream into the granulator.

There is a need in the art for alternative methods of producing a fertilizer composition containing primary fertilizer and micronized sulfur.

The essence of the invention

In one aspect, the invention includes a fertilizer composition comprising a seed particle and a coating layer comprising a water-soluble crust of dried soluble primary macronutrient fertilizer within which micronized elemental sulfur particles are dispersed. The seed particle may be solid in any desired shape or size, and may be formed according to any suitable method such as granulation or compression.

In one embodiment, the seed particle may contain urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), micronized sulfur, potassium compound, or mixtures thereof. The coating layer may contain urea, MAP, DAP, micronized sulfur, potassium compound or mixtures thereof. The primary macronutrient composition of the coating layer may be the same or different from the primary macronutrient composition of the seed particle.

In one embodiment, the composition may contain a dispersing agent in the seed particle or the coating layer, or both. The dispersant may contain an anionic, cationic, amphoteric or nonionic surfactant, or mixtures thereof.

In one embodiment, the micronized sulfur particles may have an average diameter of less than about 30 microns, and preferably less than about 10 microns.

In another aspect, the invention may include a method for preparing a fertilizer composition, which includes the steps of:

(a) obtaining a seed particle;

(b) providing a sprayable suspension containing micronized particles of elemental sulfur dispersed in a solution of primary macronutrient fertilizer to form a coating layer on the seed particle, followed by drying said coating layer to form a water-soluble crust of the dried primary macronutrient fertilizer;

(c) using a slurry to spray a coating layer of a mixture of soluble and insoluble fertilizer onto the seed particle.

In one embodiment, the seed particle itself contains fertilizer. A seed particle is preferably used to form a layer in a coating apparatus such as a rotary drum, pan granulator or fluid bed granulator, and the layer is continuously mixed using mechanical or fluid means. Preferably, the seed particle is heated using hot air to heat the layer of material to the desired temperature.

- 1 045168

Preferably, the spray slurry may be heated to achieve a higher concentration of soluble materials in the solution prior to spray coating. In one embodiment, the sprayable suspension may be sprayed through a nozzle configured in the coating apparatus to effectively coat the seed particles in the moving bed.

Brief description of the figures

In fig. 1 is a schematic representation of one example of a fertilizer production facility implementing the method of the present invention.

In fig. 2 is a schematic representation of an alternative example of a fertilizer production facility implementing the method of the present invention.

In fig. 3 is another schematic representation of another alternative example of a fertilizer production facility implementing the method of the present invention.

Detailed description

All other terms and phrases used in this description have their usual meanings as would be understood by one skilled in the art. Such ordinary meanings can be obtained by reference to technical dictionaries such as Hawley's Condensed Chemical Dictionary ^14th Edition, R. J. Lewis, John Wiley & Sons, New York, NY, 2001.

References in the description to one embodiment, embodiment, etc. indicate that the described embodiment may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but need not, refer to the same embodiment mentioned elsewhere in the specification. Moreover, when a particular aspect, feature, structure or characteristic is described in connection with one embodiment, it would be within the knowledge of one skilled in the art to combine, operate or associate such aspect, feature, structure or characteristic with any other embodiments. explicitly or implicitly described. In other words, any element or feature may be combined with any other element or feature in different embodiments only if there is no obvious or inherent incompatibility between the two, or it is specifically excluded.

As used herein, a fertilizer is any substance that contains any one of a primary macronutrient, a secondary macronutrient or a micronutrient, or combinations thereof.

In general, the invention includes a fertilizer composition comprising a seed particle spray-coated with fertilizer. The seed particle is preferably a fertilizer, and the coating may contain the same or a different fertilizer. In one embodiment, the seed particle is a solid in any desired shape or size, and can be formed by granulation, compression or pelletization.

In general, one embodiment of the method according to the present invention includes the steps:

(a) obtaining a seed particle, which may contain a primary or secondary macronutrient fertilizer or micronutrient, or combinations thereof;

(b) providing a sprayable suspension containing a solution of fertilizer in a liquid medium such as water, suspended insoluble fertilizer and a dispersing agent; and (c) using a spray suspension to spray a coating layer onto the seed particle.

The spray suspension is preferably in the form of finely divided solid fertilizer particles well dispersed in the primary fertilizer solution. Soluble fertilizer can serve as a binding agent for insoluble materials and helps form solid granules when the coating is formed. Additionally, or alternatively, coupling agents may be added to the spray slurry to help form a cohesive coating layer and promote adhesion of the spray coat layer to the seed particle.

In one embodiment, a sprayable suspension can be formed by dissolving the fertilizer in an aqueous dispersion of an insoluble fertilizer. For example, the insoluble fertilizer may contain micronized elemental sulfur formed by a process such as that described in joint US Patent Nos. 8,679,446 and 9,278,858, the entire contents of which are incorporated herein by reference, where applicable. In general, up to 85 wt.% molten sulfur is added to the superheated water, and the temperature is maintained above the melting point of the sulfur, with a dispersant concentration of from about 0.01% to about 5.0 wt.%. The mixture is then mixed or stirred to form a fine emulsion of sulfur in water. Rapid cooling of the emulsion results in solidification of the sulfur, which remains suspended in the dispersant solution, forming a micronized sulfur solid/water suspension. After the micronized sulfur has hardened, the dispersing agent can remain in solution and help

- 2 045168 in preventing agglomeration or aggregation of sulfur particles. The micronized sulfur in this solid/water suspension can then be separated from the dispersant solution to produce dispersant-coated sulfur particles. These sulfur particles can then be re-suspended and additional dispersing agent solution can be added if necessary and directly used in the next step of the present process as a solid/water slurry. In one embodiment, the solid/water suspension of micronized sulfur that results from the micronization step can be directly used in the next step of the present invention, without first separating the sulfur particles from the dispersant solution.

The dispersing agent may be a naphthalene sulfonate compound such as that found in Morwet™ or carboxymethylcellulose (CMC) or some surfactant that helps maintain the molten sulfur in a highly dispersed state before solidifying. The dispersant may be an anionic, cationic, amphoteric or nonionic surfactant, or combinations thereof. Suitable anionic surfactants include, but are not limited to, lignin derivatives such as lignosulfonates, aromatic sulfonates and aliphatic sulfonates and their formaldehyde condensates and derivatives, fatty acids/carboxylates, sulfonated fatty acids and phosphate esters of alkylphenol-, polyalkyleryl- or alkyl alkoxylates. Suitable cationic surfactants include, but are not limited to, nitrogen-containing cationic surfactants. In one embodiment, the dispersant contains a nonionic surfactant. Acceptable nonionic surfactants include, but are not limited to, alkoxylated fatty alcohols, alkoxylated fatty acids, alkoxylated fatty ethers, alkoxylated fatty amides, alcohol ethoxylates, nonylphenol ethoxylates, octylphenol ethoxylates, ethoxylated seed oils, ethoxylated mineral oils, alkoxylated alkylphenols, ethoxylated glycerides, castor oil ethoxylates, and mixtures thereof. The soluble fertilizer is then dissolved or partially dissolved in the micronized sulfur solid/water suspension to create a sprayable suspension used as a coating mixture. In one embodiment, a micronized sulfur solid/water suspension containing a dispersing agent is heated to a temperature below the melting point of the sulfur in order to dissolve more soluble fertilizers or increase the rate of dissolution. The heated slurry can also help dry the resulting granules faster.

The sprayable suspension may be applied using any conventional coating method and equipment such as a rotary drum, pan granulator or fluidized bed. Anything that constantly maintains a moving layer of solids will promote a relatively uniform spray coating application. In one embodiment, a seed particle is preferably used to form a layer in a coating apparatus such as a rotary drum, pan granulator or fluid bed granulator, and the layer is continuously agitated by mechanical or fluid means. Preferably, the seed particle is heated using hot air with the layer material to the desired temperature.

The spray suspension containing soluble and insoluble fertilizer is then sprayed through the nozzle in such a way as to effectively coat the seed particles in the moving bed. Heat can be applied simultaneously through the moving bed to evaporate the solvent and dry the granules.

In one embodiment, the spray suspension is applied as a fine spray onto the seed particle which, when dried, then leaves a hard crust of dissolved fertilizer material and embeds the suspended insoluble fertilizer carried in the spray suspension. Preferably, the seed particle is kept in constant motion, and the motion thus makes the coating process more uniform and repeatable. The sprayed suspension initially collides and adheres to the surface of the seed particle, thereby settling and building it, and continues to grow, resulting in a large granule from the coated seed particle. The coating process can continue until the granules reach the desired size corresponding to the desired nutrient analysis of N, P, K, S (nitrogen, phosphorus, potassium and sulfur).

The rate of granule growth can be controlled by adjusting process conditions such as flow rate and concentration of solution and suspension and residence time of the granule in the coating phase.

In the case of a rotating drum, the spray nozzles may be located close to the seed layer at the bottom of the drum. Nozzle placement can be chosen to keep spray output to a minimum and ensure that the spray is well dispersed and not focused on a small area. Spray nozzles can be oriented in any direction, which promotes uniform coverage of the sprayed suspension and

- 3 045168 prevents nozzles from clogging. The drum may optionally include mixing blades to facilitate rotation of the solids bed.

In the case of a fluidized bed, spray nozzles may be located within the seed bed to avoid or minimize carryover into the filter bag. Higher air velocities in the fluidized bed result in a higher transfer fraction if the nozzles are located on the outer surface of the bed. Orienting the nozzles in a suitable manner, such as horizontally with a slight downward slope, can avoid clogging of the distribution plate and clogging of the nozzle orifice due to the deposition of solid particles.

The seed particle may be obtained from any conventional production method such as pressing, granulating, pelletizing, crushing, crystallization, fluidization or the like, and the resulting seed particles may contain any shape or desired shape. The choice of the final shape and size of the final product granules can determine the shape and size of the seed particle, which in turn can influence the seed particle production process.

In one embodiment, the over- and under-lattice material from the process recycle stream may be recycled back and used to form the seed particle or be incorporated into the seed particle. Accordingly, the seed particle may contain all of the ingredients of the final product granule, including micronized elemental sulfur. This may produce a granule with two different layers, but with similar ingredients dispersed throughout the area.

The seed particle may contain none, one, or a combination of any primary or secondary macronutrient, micronutrient, or inert material. The seed particle may also contain materials impregnated with pesticides. A macronutrient fertilizer may contain potassium chloride (MOP), sulfate of potassium (SOP), urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), calcium dihydrogen phosphate or monocalcium phosphate, ammonium sulfate, ammonium nitrate, or combinations thereof. In addition, the seed particle may contain elemental sulfur, preferably in micronized form. In addition, none, one or a combination of trace minerals or secondary nutrients such as zinc, calcium, magnesium, boron, iron, copper, manganese, molybdenum, sodium, cobalt, chlorine, or selenium may be added to the mixture for inclusion in the seed particle. In one embodiment, the seed particle may be devoid of fertilizer and simply contain an inert carrier or a carrier impregnated with a herbicide or pesticide.

In one embodiment, the seed particle may comprise a combination of a powdered potassium compound (potassium chloride, potassium sulfate and/or potassium nitrate) and micronized elemental sulfur that has been compressed to form compressed mixed fertilizer seeds. The ratio of sulfur to potassium compound in the seed particle can vary from 0.1% to about 50 wt.% or more.

In another embodiment, the seed particle may comprise ammonium phosphate (MAP and/or DAP) and micronized elemental sulfur. The ratio of sulfur to ammonium phosphate in the seed particle can vary from 0.1% to about 50 wt.% or more. For example, a mixture of MAP and micronized sulfur can be formed by adding micronized sulfur before a pre-neutralizer or cross-bar reactor with phosphoric acid and ammonia, or after a pre-neutralizer or cross-piece reactor to an ammonium phosphate slurry. This suspension, containing ammonium phosphate particles and micronized sulfur particles, can then be fed to the granulator as a spray suspension during the coating stage.

The seed particle size may range from about 30 American particle size mesh (0.60 mm) to about 5 American particle size mesh (4.0 mm), and is preferably in the range of about 12 American particle size scale USP (1.70 mm) to about 8 USP mesh (2.8 mm), depending on process conditions aiding granulator growth and desired size of coated product. The desired average granule diameter in fertilizer production is generally between 1mm and 4mm.

The sprayable suspension may contain one or a combination of soluble and/or insoluble fertilizers in a liquid base. In one embodiment, the coating material may comprise a water-soluble fertilizer material in combination with an insoluble material. The insoluble material is preferably in finely divided or micronized form. The liquid spray coating base is preferably water, and may preferably contain a dispersing agent dissolved. In one embodiment, the sprayable suspension may contain dissolved urea in a concentration of up to 95 wt. % relative to water, and micronized sulfur particles. The ratio of sulfur to urea can vary from about 0.1% to about 50% by weight or more, and can be added to form a sprayable suspension of micronized sulfur in an aqueous urea solution. This sprayable suspension can then be sprayed and dried over a seed particle to grow the granule to

- 4 045168 desired size and analysis of N, K, P, S in a fluidized bed granulator.

The thickness of the spray coating may depend on the size of the seed particle and the desired size and N, P, K, S analysis of the final product. In one embodiment, the average coating thickness is preferably from about 0.30 mm to about 0.63 mm, but may range from 0.1 mm to more than 4 mm depending on the adhesive properties of the materials used in the seed and spray suspensions.

The soluble material in the sprayable suspension can also act as a binder for the insoluble materials in the suspension. This allows insoluble materials to be incorporated into the suspension and strongly adhere to the granule, thus adding the required crush strength desired in fertilizer production.

In one embodiment, using a rotating drum situation operating in a co-current or counter-current manner, spray nozzles can be located close to the seed entry point and the remaining section of the drum is used to thoroughly dry the granules in a stream of hot air. The hot air temperature can be set to the maximum possible, limited by the temperature sensitivity of the fertilizer materials and granules in order to increase thermal efficiency. The granule size can be controlled by the speed of the drum and the height of the storage ring. Typically, the spray section of the drum does not contain any blades. The drying section of the drum may preferably be equipped with paddles to facilitate better contact for faster drying.

In one embodiment, the fluidized bed may be divided into at least a spray section and a drying section. Multiple spray sections may be provided in order to facilitate larger production quantities and better maintain granulation uniformity. Likewise, multiple drying sections may be provided to achieve uniform drying at a higher throughput. The air speed can be selected depending on the density, shape and size of the seed particle fed into it. The temperature of the fluidizing air should preferably be as high as possible to minimize equipment costs, limited by the temperature sensitivity of the fertilizer and granule materials. In some cases, the fertilizer may not be temperature sensitive, but large granules may crack under the stress of a temperature gradient. The first fluidized bed section may comprise a coating section with nozzles integrated into the seed bed. The second downstream section of the bed can be used to dry the solvent to obtain a dry product.

The coated and dried product, obtained using either a rotating drum or a fluidized bed, can also be subjected to subsequent processing. In one embodiment, when using a rotating drum situation, an anti-dust agent that promotes dust control and product storage properties may be sprayed near the granule outlet or may be applied in a separate cooling drum. In another embodiment, when using a fluidized bed situation, the coating agent can be applied as a spray at the very end of the drying section, again by embedding nozzles into the solids bed to avoid carryover. In another embodiment, the coated and dried product may be glazed with either water or a soluble fertilizer solution to increase the crush strength of the product.

The concentration of solute in the sprayed suspension affects the rate of granule growth. Higher solute concentration helps the granules grow faster, thus reducing residence time and reducing energy consumption for solvent evaporation, leading to smaller, more economical equipment designs. Higher air temperature helps reduce airflow mass, thereby increasing the thermal efficiency of the system, but airflow must be balanced against the air fluidization rate required to maintain good bed expansion and efficient fluidization. Conventional urea plants use a fluidized bed granulation process for batch production. In such cases, the existing fluidized bed can be modified and upgraded to facilitate coating of the urea granules with a sprayable urea-sulfur containing slurry.

Exhaust air from the fluidized beds can be diverted to a cyclone or bag filter to purify the air before being released to the atmosphere. The collected dust can be returned back to an earlier point in the process, such as a slurry reactor or seed particle.

Thus, one granule of the finished product may contain one or more fertilizer materials, all in the desired combination and proportions, as required to make different types of products in order to meet the needs of different crops, soils and climate conditions.

- 5 045168

Examples

The following examples are intended solely to illustrate specific embodiments of the invention and not to limit the claimed invention.

Example 1. Installation diagram.

In fig. 1 is a schematic representation of a fertilizer production plant configured to implement the method described herein and produce a fertilizer composition according to the present invention. The emulsion mixing reactor (10) mixes water, nitrogen, phosphorus, or potassium (N, P, or K) macronutrient fertilizer, which may be a concentrated solution or solid granules, and either dry micronized sulfur particles or a suspension of micronized sulfur solids /water. In this case, the micronized sulfur particles have an average diameter of preferably less than about 30 microns, and more preferably less than about 10 microns.

The seed particle in the form of granules of N, P, or K (or a mixture thereof) is fed into a fluidized bed granulator (12), which includes four zones, each of which is blown with air to fluidize the particles. The seed particle first enters the first coating and drying zone (14), which uses hot air. The sprayable suspension is sprayed through nozzles in the first coating and drying zone (14). The particles migrate to a second coating and drying zone (16), which also uses hot air and also contains spray nozzles for introducing the spray suspension.

Spray coating, granule growth, and granule drying occur in the first two zones (14, 16). The particles then move to a drying zone (18) and then to a cooling and coating zone (20), where a thin dust suppressive film coating can be applied after treatment. The product to be sold is removed from the product collection (22).

Air from the fluidized bed granulator (12) is collected in a bag filter (24) where suspended fine particles are filtered or separated and collected. Depending on their composition, fine particles can be recycled to earlier stages of the process.

An alternative installation diagram is shown in Fig. 2. In reactor (100), a suspension of monoammonium phosphate and micronized sulfur in water is prepared by reacting phosphoric acid and ammonia with the addition of micronized sulfur to produce a spray suspension of dissolved MAP and suspended micronized sulfur. The sprayed suspension is then introduced into the granulator/dryer (110), along with heated air. The seed particle is introduced into the granulator/dryer (110), and the spray suspension is applied to the seed particle and dried. The resulting granules are deposited into a bucket elevator (120) and then deposited onto a vibrating screen (130) used to separate the product with a diameter in the range of 2.36-4.00 mm. The final size material is then collected, cooled and packaged. The product can also be coated during subsequent processing.

The overgrid material from the screens is sent to a hammer mill (140) or shredder and reduced to fine particles. The undersized fines are combined with the ground overgrid material and optionally a controlled final size fraction of the material and sent to a conveyor (150) where it is preheated and used as a seed particle in the granulator/dryer (110).

Dust control measures in the form of filters, drying cyclones, wet scrubbers and/or venture scrubbers are used at all stages to reduce or eliminate fugitive dust emissions.

Example 2. Preparation of micronized sulfur using nonionic surfactants.

Suitable micronized sulfur can be prepared using the methods described in joint US Pat. Nos. 8,679,446 and 9,278,858. Typically, the feed sulfur is heated to a temperature above the melting point of the sulfur such that the feed sulfur melts to form liquid sulfur. The dispersant solution is prepared at a specific concentration and heated to a temperature approximately equal to or higher than the temperature of the liquid sulfur. The dispersant solution and liquid sulfur are then mixed in a homogenizer to produce an emulsion of molten sulfur and dispersant solution. The sulfur emulsion is then cooled to solidify the sulfur and can then be directly used as a spray slurry, or can be separated and dried to leave a dry sulfur particle product that can be used to seed or resuspend and used as a spray slurry.

Table A shows examples of nonionic surfactants used as dispersants to produce micronized sulfur and particle size distribution, where PSD D50 is the particle diameter value at 50% of the cumulative distribution and PSD D95 is the particle diameter value at 95% of the cumulative distribution aggregate distribution. Table B also shows the acceptable concentration range for Triton X-405, a non-ionic surfactant. Table B also shows examples of dispersants including the situation of using an additional surfactant, anionic and nonionic surfactant.

Table A

Particle size distribution of various nonionic surfactants

Manufacturer Surface-active substance Concentration (% wt.) PSD D50 (µm) PSD D95 (µm) Dow Ecosurf (Tergitol EH-6) 2.50% 15.24 34.22 Dow Triton X405 3.00% 6.71 27.75 Dow Triton X-100 3.00% 14.52 33.02 Dow Tamol SN 3.00% 6.48 13.64 Stepan Makon 10 3.00% 11.75 41.99 Stepan Makon TD-12 3.00% 12.55 42.83 Stepan Makon TSP-16 3.00% 10.97 35.93 Stepan Polystep TSP-16 3.00% 9.18 31.78 Stepan StepFac8171 3.00% 7.11 14.75

As can be seen, each nonionic surfactant successfully produced micronized sulfur with a suitable particle size distribution.

Table B

Particle size distribution of various nonionic surfactants

Surface-active substance PSD50 (average of 2 samples) PSD95 (average of 2 samples) 5% Triton X-405 8.86 31.85 3% Triton X-405 6.71 27.75 1.50% Triton X-405 7.02 16.6 1.00% Triton X-405 8.51 23.47 0.75% Triton X-405 9.04 24.89 0.50% Triton X-405 10.85 28.78 0.25% Triton X-405 10.37 25.38 0.15% Triton X-405 9.44 29.3 0.10% Triton X-405 11.79 31.43 0.05% Triton X-405 7.84 28.9 0.30% Trinton X-405 0.60% Morwet 6.06 11.29 0.30% Triton X-405 1.80% Morwet 15.24 38.36 0.30% Triton X-405 1.50% Morwet 16.61 41.52

Suitable particle size distributions were obtained over a wide range of surfactant concentrations.

- 7 045168

Example 3: Preparation of MAP/urea granules and micronized elemental sulfur by fluid bed granulation.

A fertilizer was prepared that consisted of either urea granules or monoammonium phosphate (MAP) granules coated with a mixture of solubilized urea or MAP and micronized elemental sulfur, which was prepared as described in joint US Patent Nos. 8679446 and 9278858. Urea granules or MAP had the size distribution shown in Table. 1 below.

The sulfur was micronized and had a PSD50 of about 7 microns.

Table 1

Properties of the starting material % higher than the cell size

Free Bulk Moisture Content (%)

Sample

4750

3350

2360

2000 density (kg/m ³ )

Micron

2800

Urea and MAP particles, respectively, were used as the seed particle in the separation tests. The spray suspension was a mixture of micronized elemental sulfur, dispersant (0.001% to 5.0% (wt%)), water and either urea or MAP. Table 2 below shows the mass of material used in each run. Percentages represent ratios of solid to water. Soluble solids ranged from 40% to 80% relative to water, and insoluble solids ranged from 10% to 24% relative to soluble fertilizer. This was done in order to achieve the desired sulfur:urea and sulfur:MAP ratios.

table 2

Run solution contents

Run # Water (kg) Sulfur (kg) Urea MAP (kg) Total weight (kg) (kg)

1 73 8 (10%) 109 (60%) 0 190 2 73 16 (14%) 109 (60%) 0 198 3 55 20 (14%) 136 (70%) 0 211 4 73 12 (24%) 0 50 (40%) 135 5 110 18 (24%) 0 76 (40%) 204

Urea or MAP was slowly added to the water while the stirrer stirred the contents at high speed. When urea was mixed with water, the temperature of the solution dropped significantly. The solution required a temperature greater than about 70°C to dissolve the urea, so the solution was heated using a reactor jacket for mixing and accompanying heat control of the tubes to a temperature in the range of 85-93°C. To achieve a thick suspension and to avoid clot formation, micronized elemental sulfur powder coated with a layer of dispersing agent was slowly added to the urea solution. The stirrer speed increased as sulfur was added because the sulfur thickened the solution and the turbulence helped disperse any lumps.

A seed particle consisting of urea or MAP and a spray suspension was fed into a fluidized bed granulator FB 10 under the conditions specified in table. 3. Three urea feed test runs and two MAP feed test runs were conducted.

- 8 045168

Table 3

Run conditions

Run # Raw Material Type Speed Speed

Feeding temperature of feeding solid liquid liquid raw materials (kg/h) (kg/h) (°C)

1 Urea 95 70 102 2 Urea 96 130 90 3 Urea 96 168 91 4 IDA 95 167 85 5 IDA 94 237 79

The addition of spray slurry (liquid feed) was increased during Run 2 in order to increase the final product granule size. To start the system, the material must be preheated in three zones by activating the bag filter fan and two fluidized bed fans. The air from the fan was heated using hot generators running on natural gas. The layers were heated to about 70-90°C and, as soon as the temperature of the layer was heated, the solid particle feed mechanism (seed particle) was turned on and the spray suspension was added. One spray nozzle was used in each layer section, and the nozzles were embedded into the layer.

FB-10 successfully spray-coated seed particles to increase granule particle size and produce a urea/micronized sulfur product or a

MAP/micronized sulfur. Samples of the 5x8 mesh (US standard) product were collected for analysis during runs 2 through 5.

Table 4.1 and 4.2 below show the test results. The overgrid product was +5 mesh, the desired size product was 5x8 mesh, and the fine material was -8 mesh. Filter bag fines were taken for runs 3 and 5 and were measured to be 6 and 2 kg/h, respectively. The residence times for runs 3 and 5 were 26 and 25 minutes, respectively.

Table 4.1

Test results and product analysis

Run # Raw material type Content Free Index Index Index moisture (%) bulk overlattice product small density th product necessary product (kg/ ^m3 ) (kg/h) size (kg/h) (kg/h)

2 Urea 0.3 652 14 109 3 3 Urea 0.3 641 86 119 3 4 IDA 1.2 935 16 108 10 5 IDA 1.1 930 46 206 18

Table 4.2

Product Analysis (cont.) % above cell size

5 6 7 8 10 Micron Run # 4750 3350 2800 2360 2000 2 0.1 15.4 68.4 97.4 99.9 3 1.4 32.3 76.6 97.4 99.9 4 0.2 15.1 66.7 95.4 99.7 5 o, s 20.9 66.2 94.3 99.9

It is obvious that changes in the concentration and speed of the sprayed suspension, combined with the residence time in the fluidized bed, affect the particle size of the product. The seed particle feed rate was maintained at 94 to 96 kg/h during runs 2 to 5. There was generally an increase in granule size as the spray slurry feed rate increased.

- 9 045168

The feed rate of the atomized suspension in run 3 increased to 119 kg/h from 109 kg/h in run 2. This resulted in an increase of 10 kg/h in urea/micronized sulfur product size and 72 kg/h in overgrid urea/micronized sulfur product sulfur. Similarly, when producing the MAP/micronized sulfur product, the feed rate of the spray slurry was increased from 167 kg/h (Run 4) to 237 kg/h (Run 5), and the desired product size increased by 98 kg/h, while the of over-grid product increased by 30 kg/h. Thus, increasing the MAP/micronized sulfur treatment fluid rate resulted in a 90% increase in 5x8 mesh product yield, while increasing the urea/micronized sulfur treatment fluid rate resulted in a 9% increase in 5x8 mesh product yield. For the urea/micronized sulfur process, the lower increase in target size yield was due in part to the larger increase in the over-grid fraction.

Samples from all three product zones were taken during runs 2, 3, and 5. Moisture content for each layer zone was also analyzed and presented in Table 1. 5 below.

Table 5

Run conditions

Chemical analysis of the products was carried out in accordance with the methods of the Association of Public Service Chemical Analysts (AOAC). Product samples were tested for total nitrogen, total _P2O5 , K2O, total S and _moisture .

Chemical analysis of the resulting 5x8 mesh phosphate/micronized sulfur product showed 11.7% total nitrogen, 46.6% P ₂ O ₅ , and 5.0% total sulfur. Analysis of the phosphate/micronized sulfur 5+ mesh product showed total nitrogen - 11.1%, P ₂ O ₅ - 50.3%, and total sulfur - 5.0%.

Chemical analysis of the resulting urea/micronized sulfur 5x8 mesh product showed 44.1% total nitrogen and 4.5% total sulfur. Analysis of the urea/micronized sulfur 5+ mesh product showed 43.0% total nitrogen and 8.9% total sulfur.

Physical properties studies were carried out on the products in accordance with the Guidelines for the Determination of Physical Properties of Fertilizers (IFDC-R-10).

The selected physical properties that were determined were granule crush strength (IFDC S115), and abrasion strength (IFDC S116).

Granule crush strength for the urea/micronized sulfur product ranged from 2.86 to 3.39 kg/pellet. Granule crush strength for the phosphate/micronized sulfur product ranged from 8.67 to 9.90 kg/pellet. The abrasion resistance of both products meets acceptable criteria.

Another study consisting of urea granules mixed with micronized elemental sulfur was also completed using a higher concentration of urea in a spray suspension. The spray suspension in this study was a mixture of urea and micronized elemental sulfur, coated with a layer of dispersing agent in the quantities shown in table. 6. Soluble urea ranged from 85 to 95% relative to water, and insoluble micronized elemental sulfur ranged from 14% to 17% relative to soluble urea.

Table 6

Liquid Feed Series Material Ratio

Run # Sulfur:Urea Urea:H ₂ Total mass per (%) O (%) (kg)

1 14 90 260 (571 lbs) 2 17 90 134 (295 lbs) 3 17 85 213(468 lbs)

When mixing the materials using a stirrer, the temperature was maintained at 80-100°C to allow the urea to dissolve. The seed particle and the sprayed suspension were fed into a fluidized bed granulator FB 10 under the conditions specified in table. 7.

- 10 045168

Table 7

Run conditions

Run # Speed Speed Temperature Gas supply supply temperature solid liquid liquid (°C) inlet raw material (kg/h) (kg/h) nozzle (°C) 1 48 41 106 144 2 49 41 106 21 3 73 86 99-100 169

Table 8 shows the results of the study. After running the process for about 1 hour, the product rate and the recycle feed rate were almost the same, allowing pure urea to be supplied as a seed particle to be replaced by the recycle feed. The last rate recorded for the recirculation feed was 73 kg/h, and 75 kg/h for the 5x8 mesh product. Ideally, with a liquid feed rate of 91 kg/h and a solids feed rate of 80 kg/h, by controlling the moisture loss from fluidized bed drying, the 5x8 mesh product rate and the combined overgrid and fine material rates would be 80 kg/h each. Although the feed rate could be stabilized, the process would need to be carried out over a longer period of time to allow the recirculating feed to consist of the same analyzed N, P, K, S as the sprayed suspension in order to obtain homogeneous fertilizer product.

Table 8

Research Results and Product Analysis % Above Cell Size

4 5 6 8 10 12 20 nasy % Above micron size other Run sample 4750 4000 3350 2360 2000 1700 850 flesh bone (g/cm ³ ) 3 5x8 mesh FB product 0 0.4 20.4 88.7 99.7 - 100.0 0.663 3 5x8 mesh FB product 0 0.4 17.9 86.7 99.8 - 100.0 0.614 3 Unsifted FB product 2.1 7.4 14.9 36.7 65.5 - 100.0 0.625 3 Shredded overlattice +recyclized small material 0.3 0.5 0.8 1.7 16.9 54.8 99.9 0.710

Chemical analysis of urea/micronized sulfur products was carried out in accordance with the methods of the Association of Analytical Chemists in Public Service (AOAC). Product samples were tested for total nitrogen, total _P2O5 , K2O, total S, and moisture.

Chemical analysis of the resulting urea/micronized sulfur product from Run #3 showed 41.7% total nitrogen and 10.1% total sulfur.

Physical properties studies were carried out on the urea/micronized sulfur product in accordance with the Guidelines for the Determination of Physical Properties of Fertilizers (IFDC-R-10). The selected physical properties that were determined were the crushing strength of the granule

- 11 045168 (IFDC S115), and abrasion resistance (IFDC S116).

Granule crush strength for the urea/micronized sulfur product ranged from 3.58 to 3.92 kg/pellet. Abrasion resistance met acceptable criteria.

Example 3. Preparation of MAP granules and micronized sulfur by drum granulation.

The fertilizer, consisting of MAP and micronized elemental sulfur, was produced by starting with phosphoric acid and ammonia as raw materials and using a modified rotary drum dryer as granulation and drying equipment.

MAP particles were used as a seed particle to begin with, but were replaced with MAP/micronized sulfur for recycle feed once the process had stabilized the product rate and recycle feed. The sprayed suspension was obtained in a preliminary neutralizer, into which commercial grade phosphoric acid and ammonia were loaded in a 1:1 molar ratio. Filtered and dried micronized sulfur coated with a dispersant was then added at about 15 wt.% and 22 wt.% relative to MAP.

A spray suspension of dissolved MAP and micronized sulfur was then sprayed into a rotating drum to coat the seed particle under conditions where it was heated and dried. The rotating drum was divided into a feeding/spraying section and a drying section using an internal water retaining baffle. The feeding/spraying section was smooth, while the drying section used lifting paddle nozzles to cascade the granules. The heated air flowed directly through the rotating drum. The rotating drum was operated at an inclination angle of 2.0°, and the rotation speed was set to 12 rpm.

The granules from the rotating drum were transferred to a vibrating screen using a centrifugal bucket elevator. The 4mm oversize and 2.36mm undersieve produced product in the desired size range. The overgrid material was sent to the hammer mill, crushed and mixed with the material passing through the screen, and returned back to the feed section of the rotating drum as a seed particle.

The product granules of the desired size were cooled using a direct air flow and collected in bags. A certain amount of the product was further dried in a rotary drum dryer.

Chemical analysis of the phosphate/micronized sulfur products was carried out in accordance with the methods of the Association of Analytical Chemists in Public Service (AOAC). Product samples were tested for total nitrogen, total _P2O5 , K2O, total S, and _moisture . Chemical analysis of the resulting phosphate/micronized sulfur product showed total nitrogen - 9.3%, P ₂ O ₅ - 48.5%, and total sulfur - 13.8%. In a separate run, the concentration of micronized sulfur in the MAP/sulfur slurry increased and nutrient analysis showed 8.4% total nitrogen, 43.0% P ₂ O ₅ , and 21.1% total sulfur. By stabilizing the product rate and recirculating the feed over a period of time, the N, P, K, S analysis is expected to stabilize to produce a uniform fertilizer product that consists of the original wt.% micronized sulfur introduced into the process.

Physical properties studies were carried out on the products in accordance with the Guidelines for the Determination of Physical Properties of Fertilizers (IFDC-R-10). The selected physical properties that were determined were dry sieving size analysis (IFDC S107, Procedure 1), granule crush strength (IFDC S115), and abrasion strength (IFDC S116).

Size analysis of fertilizer products is defined as the range of particle diameters of the material. It is typically measured by sieving, the process of separating a mixture of particles according to their size fraction. Size analysis performed on product samples indicated that all sieved phosphate/micronized sulfur products had greater than 98.2% granules retained between the 2.00 mm and 4.00 mm sieves.

The granule crush strength ranged from 0.67 to 2.57 kg/pellet before the drying step, from 1.65 to 3.51 kg/pellet after the drying step. Abrasion resistance met acceptable criteria.

Example 4. Preparation of potassium compound/micronized sulfur granules by drum granulation.

A fertilizer consisting of a sulfur compound and micronized elemental sulfur was prepared by starting with potassium chloride and micronized elemental sulfur as raw materials, and using a modified rotary drum dryer as granulation and drying equipment.

Large potassium chloride (KCl) particles were used as a seed particle to begin with, but were replaced with recycled KCl/micronized sulfur feed material once the process stabilized the product rate and recycled the feed material. The sprayed suspension consisted of a mixture of dissolved KCl and 15 wt.% micronized elemental sulfur. The KCl solution was maintained above 95 °C in order to maintain the concentration of the KCl solution at least 34% K2O. The reactor for micronized sulfur suspension was equipped with a stirrer in order to

- 12 045168 maintain sulfur in a well-dispersed state.

Granulation of the material took place in a rotating drum type dryer by spraying a nebulized KCl/micronized sulfur suspension into the granulator/dryer. The rotary drum type dryer had a smooth section with a water retaining baffle for the first one third of the dryer, and the remaining two thirds of the dryer had lifting paddle attachments. The material in the first third of the granulator/dryer formed a rolling bed with a slurry that was sprayed over the top of the bed to form granules. The spray slurry was sprayed into the granulator/dryer through the outlet of a spray nozzle positioned so that the slurry was sprayed onto the bed of material in the first section. The second section of the granulator/dryer, containing lifting paddle attachments, created cascades of material that were dried using a direct flow of air. The natural gas combustion chamber was located at the inlet (material feed end) of the granulator/dryer. The operating temperature of the granulator/dryer was controlled indirectly by measuring the temperature of the granulator/dryer outlet material and adjusting the combustion chamber air-gas ratio to maintain the desired operating temperature. The granulator/dryer was operated at an inclination angle of 2.0 degrees from horizontal, and the rotation speed of the granulator/dryer was maximum at 12 revolutions per minute (rpm). The granulator/dryer was equipped with two rows of hammers, each row containing four hammers.

A cyclone type dust collector was located in the exhaust air/gas duct between the granulator/dryer outlet and the granulator/dryer exhaust fan. The granulator/dryer fan vents to the wet scrubber and then to the atmosphere.

A centrifugal type bucket elevator was used to transfer material from the granulator/dryer outlet to a rotating drum type process cooler. The process cooler operated with countercurrent air flow. A cyclone-type dust collector was located in the air exhaust duct between the process cooler air outlet and the exhaust fan. The process cooler was operated at an inclination angle of 2.0° from the horizontal.

The screen body was equipped with a bonded square mesh oversieve (4.0mm [mm] opening) and a bonded square mesh undersieve (2.36mm opening) in order to obtain a product with a size range of 2.36 to 4. 00 mm. The overgrid material from the screening system was sent to a hammer mill. The crushed material discharged from the hammer mill was returned (recirculated) to the conveyor along with the screened material from the screening system and a controlled fraction of the correct size product material when needed to maintain granulation control. The product fraction of the required size was fed into the product cooler, which operated at a rotation speed of 9 rpm. The product material of the required size was collected in bags.

Dust from the elevators, screening systems, product cooler and conveyors was collected by a blown dust collection system. Gases from the process cooler passed through a cyclone-type dust collector located in the exhaust air/gas duct between the cooler outlet and the cooler exhaust fan before being vented to the atmosphere.

Chemical analysis of the potassium compound/micronized sulfur products was carried out in accordance with the methods of the Association of Analytical Chemists in Public Service (AOAC). Product samples were tested for total nitrogen, total _P2O5 , K2O, total S and _moisture .

Chemical analysis of each of the composite sample products indicated that total sulfur ranged from about 13.2% to about 15.0% and K2O was 52.1% K2O. By stabilizing the product rate and recirculating the feed over a period of time, the N, P, K, S analysis is expected to stabilize to produce a uniform fertilizer product that consists of the original wt.% micronized sulfur introduced into the process. The moisture content of all analyzed products was less than 0.1%.

Physical properties studies were carried out on potassium compound/micronized sulfur products in accordance with the Guidelines for the Determination of Physical Properties of Fertilizers (IFDC-R-10). The selected physical properties that were determined were dry sieving size analysis (IFDC S107, procedure 1), granule crush strength (IFDC S115), and abrasion strength (IFDC S116).

Size analysis of fertilizer products is defined as the range of particle diameters of the material. It is typically measured by sieving, the process of separating a mixture of particles according to their size fraction. Size analysis carried out on product samples showed that all sifted products had more than 97.5% granules retained between the 2.00 mm and 4.00 mm sieves.

Crushing strength is defined as the minimum force required to crush individual particles. Crushing strength is measured by applying pressure to individual granules - typically a specific size range (-2.80 mm + 2.36 mm) - and recording the pressure required to crush each granule. Pellet crushing strength was used to predict the expected handling and storage properties of the granules and the pressure limits applied

- 13 045168 during the storage of bags and bulk materials.

The average crush strength of the potassium compound/micronized sulfur products ranged from about 1.54 to about 2.35 kg/pellet.

Abrasion resistance is the resistance to dust and fine particle generation and pellet breakdown resulting from pellet-to-pellet and pellet-to-equipment contact during processing. Abrasion resistance is determined by measuring the percentage of dust and fine particles (percentage attrition) generated when the sample is subjected to an abrasive type of action. The abrasion strength for the two products studied ranged from about 3.42% to about 3.90% of fracture.

Definitions and interpretation.

The description of the present invention has been provided for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in its disclosed form. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The embodiments have been selected and described to better explain the principles of the invention and practical application, as well as to enable others skilled in the art to understand the invention for various embodiments with various modifications as are appropriate for the particular use contemplated.

The respective structures, materials, actions and equivalents of all means or steps plus functional elements in the claims appended to this specification are intended to include any structure, material or action to perform a function in combination with other claimed elements as specifically claimed.

It is further noted that the claims may be drafted to exclude any optional element. Thus, this summary is intended to serve as a precursor to the use of exclusive terminology, such as exclusively, only, etc., in connection with the recitation of claims or the use of a negative limitation. The terms preferably, preferred, prefer, optional, may, and similar terms are used to indicate that the item, condition, or step referred to is an optional feature of the invention.

Singular forms include reference to the plural unless the context clearly dictates otherwise. The term and/or means any one of the items, any combination of items, or all of the items with which the term is associated. The term and/or means any one of the items, any combination of items, or all of the items with which the term is associated. The phrase one or more is easily understood by one skilled in the art, especially when read in the context of its use.

As will be appreciated by one skilled in the art, all numbers, including those expressing quantities of reactants or ingredients, properties such as molecular weight, reaction conditions, and the like, are approximations and are understood to be those that are optionally modified in all cases by term about. These values may vary depending on the desired properties that are sought to be obtained by those skilled in the art using the teachings of the description herein. It is also understood that such values inherently contain variability that inevitably arises as a result of the standard deviations found in their respective study measurements.

The term about may refer to a variation of ±5%, ±10%, ±20%, or ±25% of the specified value. For example, about 50 percent may in some embodiments range from 45 to 55 percent. For integer ranges, the term about may include one or two integers greater than and/or less than the listed integer at each end of the range. Unless otherwise specified herein, the term about is intended to include values and ranges close to the stated range that are equivalent in terms of the functionality of the composition or embodiment.

As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges given herein also include any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values that make up a range, particularly integer values. The highlighted range (eg, weight percentages or carbon groups) includes each specific value, integer, decimal, or identity within the range. Any range listed can easily be recognized as being sufficiently descriptive to allow the same range to be broken down at least in half, into three, four, five or ten parts. As a non-limiting example, each range discussed herein can be easily broken down into a lower third, a middle third, and an upper third, etc.

One skilled in the art will also understand that all statements such as up to at least more than, less than, more than, or more than and the like include the specified

-

Claims (14)

number, and such terms refer to ranges, which can then be broken down into subranges as discussed above. In the same way, all relationships given herein also include all subratios that fall within the broader relationship. Accordingly, the specific values given for radicals, substituents and ranges are for illustration purposes only; they do not exclude other specified meanings or other meanings within certain ranges for radicals and substituents. One skilled in the art will also readily appreciate that if the members are grouped together in a general manner, such as in the Markush group, the invention covers not only the entire group listed as a whole, but each member of the group individually and all possible subgroups of the main group. Moreover, for all purposes, the invention covers not only the main group, but also the main group in which one or more group members are missing. Therefore, the invention provides for the express exclusion of any one or more members of the above group. Accordingly, disclaimers may apply to any of the disclosed categories or embodiments, provided that any one or more of the disclosed elements, types or embodiments may be excluded from such categories or embodiments, for example, as used in an express negative limitation. CLAIM 1. A method for producing a solid fertilizer particle, comprising the steps of spray coating a seed particle with a sprayable suspension containing micronized particles of elemental sulfur dispersed in a solution of a primary macronutrient fertilizer to form a coating layer on the seed particle, and subsequent drying of said coating layer to form a water-soluble a crust of dried primary macronutrient fertilizer, within which micronized particles of elemental sulfur are dispersed, wherein said crust contributes to the resistance of the granules to crushing and reduces dust formation, as well as the rapid release of micronized elemental sulfur, which reduces the time when the fertilizer becomes available to plants. 2. The method according to claim 1, characterized in that the seed particle contains a primary macronutrient fertilizer. 3. The method according to claim 1 or 2, characterized in that the seed particle contains micronized sulfur particles mixed with primary macronutrient fertilizer. 4. Method according to claim 1, 2 or 3, characterized in that the seed particle contains urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), micronized sulfur or potassium compound or mixtures thereof. 5. Method according to claim 1, 2, 3 or 4, characterized in that the spray coating step takes place in a rotating drum or fluid bed granulator. 6. The method according to claim 4, characterized in that the sprayed suspension contains the same primary macroelement or combination of macroelements as the seed particle. 7. The method according to any one of claims 1 to 6, characterized in that the sprayable suspension is obtained by emulsifying liquid sulfur in a dispersing agent solution, cooling the emulsion to obtain a suspension of micronized elemental sulfur and dissolving the primary macroelement in the suspension. 8. The method according to claim 7, characterized in that the dispersing agent contains an anionic, cationic, amphoteric or nonionic surfactant or mixtures thereof. 9. The method of claim 1, further comprising the step of grinding the over-grid portion of the product and combining it with a portion of the material passing through the screen to form seed particles, and recycling the seed particles to the spray coating step, wherein the spray coated particles are screened to providing a desired size portion of the product, an over-grid portion, and a portion of the material passing through the screen, wherein spray-coating the seed particle includes spray-coating a plurality of seed particles to produce a plurality of spray-coated particles. 10. Method according to any one of claims 1 to 9, characterized in that the fertilizer particle is subjected to subsequent processing to increase hardness and/or dust suppression. 11. Method according to any one of claims 1 to 10, characterized in that the trace element is added to the seed particle or the spray suspension or both. 12. The method according to any one of claims 1 to 11, characterized in that the micronized particles of elemental sulfur have an average diameter of less than about 30 microns. 13. The method of claim 12, wherein the micronized elemental sulfur particles have an average diameter of less than about 10 microns. 14. The method according to claim 4, characterized in that the sprayed suspension contains a primary macroelement different from the seed particle. -