Method and compositions for urea-potassium chloride pastille fertilizer

Abstract

The present invention relates to the field of agriculture, specifically to the composition and production of fertilizers. It relates to a novel fertilizer pastille composition that contains urea and potassium chloride or similar materials in a stable and efficient form. The invention focuses on challenges associated with urea-potassium chloride pastilles fertilizer production, such as hygroscopicity, nutrient uniformity, mechanical strength, and molten mix pastillation processes.

Description

Method and compositions for urea-potassium chloride pastille fertilizer

[0001] The present invention relates to the field of pastille fertilizer compositions, specifically to production of Urea and potassium chloride composite fertilizer through molten mix roto form pastillation.

[0002] Modern agriculture depends on fertilizers to supply essential major nutrients such as nitrogen (N), potassium (K), which are necessary for optimal crop growth and yield. While soil naturally contains these nutrients, their levels are often inadequate to support the high demands of modern high-yield farming systems. This makes fertilizers a critical input for sustainable agricultural productivity.

[0003] The three primary macronutrients supplied by fertilizers nitrogen (N), phosphorus (P), and potassium (K) are typically delivered in customized formulations tailored to specific crop and soil requirements. Among these, nitrogen plays a vital role in vegetative growth, while potassium enhances water retention, disease resistance, and overall plant health.

[0004] Urea is the most widely used nitrogen fertilizer due to its high nitrogen content and cost-effectiveness. Similarly, potassium chloride (commonly referred to as muriate of potash, or MOP) is a preferred potassium source because it provides readily water-soluble potassium and chloride ions essential for plant growth. However, combining urea and potassium chloride into a single, stable fertilizer formulation has long been a significant challenge due to the technical issues:

[0005] Both urea and potassium chloride are highly hygroscopic, readily absorbing moisture from the atmosphere. This leads to caking, dissolution, and instability during storage and handling, making it difficult to maintain product quality.

[0006] A uniform blend of urea and potassium chloride within a composite fertilizer is critical for consistent nutrient delivery to plants. Achieving this uniformity in solid forms, such as pastilles or granules, is technically complex due to differences in material properties.

[0007] Urea and potassium chloride fertilizers generally show poor mechanical strength. Therefore, fertilizers must have sufficient mechanical strength to maintain their structural integrity during handling, transport, and application. Weak fertilizers are prone to breakage, resulting in uneven nutrient distribution in the field, reduced crop yield, and financial losses for manufacturers and farmers.

[0008] Producing consistent, near-spherical pastilles using molten mix technology requires overcoming material incompatibilities and achieving precise temperature control. Maintaining molten mix consistency during this process is critical for producing a quality product.

[0009] To address these challenges, there is a growing demand for fertilizers that integrate nitrogen and potassium into a single, stable formulation. Such fertilizers must provide consistent nutrient release, withstand environmental and mechanical stresses, and reduce environmental impacts, such as ammonia volatilization and nutrient leaching.

[0010] Advanced fertilizer technologies, including composite materials, controlled-release systems and coated formulations, have shown potential to meet these demands by improving nutrient use efficiency and supporting sustainable farming practices. The disclosed invention aims to address these technical challenges by developing a novel urea-potassium chloride pastille formulation.

[0011] Invention discloses a novel fertilizer pastille product that combines urea and potassium chloride (or similar materials from synthetic or natural sources) with optional additional nutrients and coating layers.

[0012] Urea is present in an amount of 25% to 75% by weight, preferably 50% to 70% by weight, and more preferably 60% to 70% by weight. Potash-containing materials are included in an amount of 10% to 50% by weight, preferably 20% to 40% by weight, and more preferably 5% to 30% by weight. A binder is present in an amount of 0.5% to 5% by weight, preferably 0.5% to 2% by weight, and more preferably 1% to 2% by weight. Surfactant materials are included in an amount of 0.2% to 4% by weight, preferably 0.2% to 2% by weight, and more preferably 0.5% to 1% by weight.

[0013] Optional additives, such as plant growth regulators, hydrogels, nutrients, pesticides, or any agriculturally relevant materials, are present in an amount of 1% to 10% by weight, preferably 2% to 6% by weight, and more preferably 5% to 10% by weight for enhanced performance.

[0014] The pastille contains a homogeneous distribution of all nutrient materials, preferably urea-potassium chloride, within a composite matrix. Additionally, one or more coating layers, composed of inorganic or organic materials such as metal chalcogenides, silicates, long-chain nonpolar lipids, or any agriculturally relevant materials, are present in amounts of 0.1% to 10% by weight, preferably 3% to 8% by weight, and more preferably 1% to 5% by weight. These coatings reduce hygroscopicity, improve storage properties, and enable controlled or sustained release of nutrients and delivery of agricultural inputs through the coating platform.

[0015] The key challenges in combining urea and potassium chloride into a stable fertilizer formulation are multifaceted. Both materials are highly hygroscopic, causing caking, dissolution, and instability during storage. Achieving a uniform nutrient blend is complex due to their differing properties, while poor mechanical strength leads to breakage during handling and uneven nutrient distribution. Additionally, material incompatibility in molten mix production and precise temperature control makes pastille formation difficult.

[0016] The invention addresses the challenges of hygroscopicity, nutrient uniformity, mechanical strength, and molten mix roto-form pastillation in fertilizer compositions, providing an efficient and stable solution for fertilizer use.

[0017] This invention provides a practical solution for combining urea and potassium chloride into a stable, high-performance fertilizer for modern agricultural applications. Its benefits include: (i) ensuring uniform distribution of nutrients within the pastilles for consistent plant absorption, (ii) enhancing stability and shelf life through hydrophobic coatings that minimize moisture absorption, (iii) compatibility with various halide materials and additional nutrients for customization to specific crop needs, and (iv) optimizing nutrient delivery while reducing waste and environmental impact.

[0018] shows a representative image of the urea-potassium chloride fertilizer pastilles compositions.

[0019] The present invention relates to a method for producing urea-potassium chloride pastille fertilizer compositions with improved mechanical properties and reduced hygroscopicity. The pastilles maintain their size and shape during handling and use by the end user. After application, the pastilles disperse quickly upon contact with moisture from natural precipitation or soil. This dispersion causes the potassium chloride to dissolve rapidly, releasing the urea and other active ingredients into the soil, making them gradually available to plants.

[0020] The terms "disperse," "dissolve," and "release" in the context of the present invention refer to the pastilles breaking down into finely divided sub-particles upon contact with moisture. This process allows the potassium chloride molecules to dissolve into ions, releasing the urea, surfactant, and binder molecules.

[0021] In one embodiment, the composition of the pastilles includes urea, potassium chloride, a binder, and a surfactant. The total composition can be prepared using a melt emulsification process such as a roto-moulding pastillation process, a melt blending process, or high-shear mixing. In a preferred embodiment, the pastille size ranges from 1 to 5 mm, with a more specific preference for 2 to 4 mm.

[0022] In another embodiment, the pastilles comprise urea and potassium chloride salts that provide nitrogen and potassium nutrients. Urea is present in an amount of 25% to 75% by weight, preferably 50% to 70%, and more preferably 60% to 75% of the total dry weight of the pastilles. The salts providing potassium, chloride, and other nutrients are included at 10% to 50% by weight, preferably 20% to 40%, and more preferably 5% to 30% of the total dry weight of the pastilles. Specific salts may include, but are not limited to, potassium chloride, as well as other halides such as ammonium chloride, calcium chloride, magnesium chloride, and sodium chloride.

[0023] In one embodiment, the binder component is present in an amount of 0.5% to 5% by weight, preferably 0.5% to 2%, and more preferably 1% to 2% by weight of the total dry weight of the pastilles to improve the flow and consistency of the mixture. Examples of suitable binders include cellulose and cellulose derivatives, such as carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxyethylpropylcellulose, and methylhydroxyethylcellulose. Starch and starch derivatives, such as amylose, starch acetate, starch hydroxyethyl ether, ionic starch, long-chain alkyl starch, dextrin, and vegetable starches (e.g., corn starch and potato starch), are also effective. Other carbohydrates include pectin, amylopectin, xylan, glycogen, agar, alginic acid, phycocolloids, chitin, gum arabic, guar gum, and karaya gum. Lignin and lignin derivatives such as nitrolignin, and lignin sulfonates (e.g., calcium lignosulfonate, ammonium lignosulfonate, and sodium lignosulfonate) are also suitable.

[0024] In another embodiment, Complex carbohydrates like molasses, proteins such as soybean extract, zein (corn protein), prolamins, collagen, gelatin, and casein can also serve as binders. Synthetic organic polymers such as ethylene oxide polymers, polyacrylamides, polyacrylates, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinyl methyl ether, polyvinyl acrylate, polylactic acid, and latex are effective.

[0025] In another embodiment, silicates can also be used as binders. Examples include sodium metasilicate, sodium orthosilicate, potassium silicates (e.g., potassium metasilicate and potassium orthosilicate), lithium silicates (e.g., lithium metasilicate and lithium orthosilicate), calcium silicates (e.g., calcium metasilicate and calcium orthosilicate), aluminium silicates (e.g., kaolin, montmorillonite, bentonite, and zeolite), magnesium silicates (e.g., talc, serpentine, and olivine), and zirconium silicates (e.g., zirconium orthosilicate). In a preferred embodiment, silicates, particularly aluminium silicates such as kaolin, montmorillonite, bentonite, and zeolite, are especially effective as binders, either alone or in combination with other binder types.

[0026] In another embodiment, the pastille fertilizer composition contains a surfactant that promotes wetting and dispersion of the urea-potassium chloride-binder in the molten stage. The surfactant is present in in an amount of 0.2% to 4% by weight, preferably in an amount of 0.2% to 2% by weight and more preferably in an amount of 0.5% to 1% by weight of the total dry weight of the pastilles. Examples of suitable surfactants are non-ionic surfactants such as alcohol ethoxylates (Lauryl alcohol ethoxylate), alkylphenol ethoxylates( nonylphenol ethoxylates and octylphenol ethoxylates) , fatty acid esters( Sorbitan esters e.g., Span 20, 40, 60, 80, ethoxylated sorbitan esters e.g., Tween 20, 40, 60, 80, and glycerol esters, alkyl polyglucosides (Decyl glucoside); anionic surfactants such as lgnosulfonates, sulfates and sulfonates (alkyl sulfates , alkyl ether sulfates , and alpha-olefin sulfonates, odium lauryl sulfate , sodium laureth sulfate, phosphate esters (Potassium butyl phosphate); cationic surfactants such as quaternary ammonium compounds (cetrimonium chloride and benzalkonium chloride), amine ethoxylates; amphoteric surfactants such as betaines (cocamidopropyl betaine and lauryl betaine), amine oxides (Lauramine oxide)

[0027] In another embodiment, the pastille contains agricultural nutrients, biostimulants, hydrogels, plant growth regulators, pesticides, or other agriculturally relevant substances in an amount of 1% to 10% by weight, preferably 2% to 6% by weight, and more preferably 5% to 10% by weight of the total dry weight of the pastille, to improve its value and performance. In a preferred embodiment, the pastille contains a binder that creates or promotes the aggregation of the urea-potassium chloride material.

[0028] In an embodiment, an exemplary urea-potassium chloride pastille fertilizer composition is produced by preparing a molten urea-potassium chloride salt mixture. The molten urea-potassium chloride may first be mixed with one or more combinations of binder and surfactant materials; any other mixing order would not depart from the scope of the present invention. The urea-potassium chloride pastille fertilizer can be produced in a batch process or a continuous production line.

[0029] In one embodiment, the urea is transported to a urea melter system and transferred to a mixing tank, where the potassium chloride material is gradually added to the molten urea. In one embodiment, the binder and surfactant materials are added to the continuously stirred urea-potassium chloride molten mixture or are premixed with the potassium chloride material. The molten mixture may be mixed for approximately 1 minute to 5 hours, preferably 10 minutes to 2 hours, more preferably 5 minutes to 1 hour, and most preferably 10 to 30 minutes. Heat is added to maintain the mixture above its molten state during the mixing process.

[0030] In another embodiment, after mixing, the molten mixture can be homogenized using a homogenizer, high-shear mixer, or other mixing system. The homogeneously dispersed molten mix of urea-potassium chloride-binder-surfactant (or other materials) is then transferred to a feeding tank while maintaining the desired temperature.

[0031] In one embodiment, the homogeneously dispersed molten mix is pumped from the mixing or feeding tank through a filter with a pore size suitable for the raw materials or additives, preferably less than 300 microns. The filtered mixture is then processed using a roto-form pastillation system, where the pastilles are harvested.

[0032] In one embodiment, the molten mix, referred to as the medium, contains urea, potassium chloride, binder, and surfactant materials.

[0033] In another embodiment, one or more hydrophobic coating layers comprising inorganic or organic materials, such as metal chalcogenides, silicates, and lipids (e.g., mineral oils, essential oils, oils and fats, and waxes), alone or in combinations, are applied. These coatings are present in an amount of 0.1% to 10% by weight, preferably 3% to 8% by weight, and more preferably 1% to 5% by weight of the total dry weight of the pastille. The coating reduces hygroscopicity, improves storage properties, and enables controlled or sustained release of nutrients and agricultural inputs via the coating platform. The coated pastille fertilizer composition may also demonstrate enhanced agronomic performance.

[0034] In another embodiment, the composition reduces urea loss and enhances use efficiency by decreasing ammonia (NH3) volatilization through the concurrent application of potassium chloride, which temporarily reduces soil pH. Additionally, the composition mitigates soil nitrogen and potassium leaching, addressing associated pollution problems.

[0035] In another embodiment, Pastilles are a formulation composed of granules derived from a molten mix of urea, potassium chloride, binder, and surfactant. These granules can be applied to soil using basal or top-dress application methods. Once exposed to moisture or water in the soil, the pastilles break down and disperse effectively.

[0036] In another embodiment, the moisture content in the finished pastille product is within the range of 1% to 2% by weight, with a preferred range of 0.4% to 1.0% by weight.

[0037] In one embodiment, the proportions of the molten mix of urea, potassium chloride, binder, and surfactant materials are determined based on the viscosity after homogenization or high-shear mixing, ensuring that the mixture remains pumpable in its molten state for production using a roto-form pastillator.

[0038] In one embodiment of this invention, the molten mix of urea, potassium chloride, binder, and surfactant materials are prepared at atmospheric pressure.

[0039] The process consists of the following steps:

[0040] Step 1: Urea, in an amount of 25% to 75% by weight, preferably 50% to 70% by weight, and more preferably 60% to 70% by weight, is melted in a urea melter system at a temperature maintained between 130°C and 140°C.

[0041] Step 2: The melted urea is transferred into a mixing tank, where potassium chloride material is added in an amount of 10% to 50% by weight, preferably 20% to 40% by weight, and more preferably 5% to 30% by weight. The temperature is maintained between 100°C to 150°C. This process produces a urea-potassium chloride molten mix, which is stirred for 0.1 to 2 hours at 40 RPM. These conditions ensure even mixing of urea molecules and potassium chloride salt in the molten state.

[0042] Step 3: Binding materials, in an amount of 0.5% to 5% by weight, preferably 0.5% to 2% by weight, and more preferably 1% to 2% by weight, are added to the urea-potassium chloride molten mix from Step 2. The mixture is stirred for 0.1 to 1 hour at 40-300 RPM at a temperature of 100°C to 150°C, allowing the binder materials to disperse into the molten urea-potassium chloride medium. This results in a molten urea-potassium chloride-binder mix.

[0043] Step 4: Surfactant materials, in an amount of 0.2% to 4% by weight, preferably 0.2% to 2% by weight, and more preferably 0.5% to 1% by weight, are added to the urea-potassium chloride-binder mix from Step 3. The mixture is stirred for 0.1 to 1 hour at 40-300 RPM at a temperature of 100°C to 150°C, resulting in a molten urea-potassium chloride-binder-surfactant mix.

[0044] Step 5 (Optional): To enrich the composition, plant growth regulators, hydrogels, nutrients, pesticides, or other agriculturally relevant materials, in an amount of 1% to 10% by weight, preferably 2% to 6% by weight, and more preferably 5% to 10% by weight, can be added to the molten urea-potassium chloride-binder-surfactant mix from Step 4. The mixture is stirred for 0.1 to 1 hour at 40-300 RPM at a temperature of 100°C to 150°C, resulting in a molten urea-potassium chloride-binder-surfactant-value additives mix.

[0045] Step 6: The molten urea-potassium chloride-binder-surfactant-value additives mix from Step 5 is pumped into a roto-form pastillator to produce the pastille-form fertilizer composition.

[0046] Step 7: The pastille composition produced in Step 6 is coated with a formulation or agriculturally relevant materials in an amount of 0.1% to 10% by weight, preferably 3% to 8% by weight, and more preferably 1% to 5% by weight.Examples

[0047] Example Compositions: The described inventive process is further clarified by the following example compositions.

[0048] Example 1. (30 N+16 K)IngredientsQuantity (Kg) required to produce one metric ton productUrea650 KgPotassium chloride329Binder20 kgSurfactant1Kg

[0049] Example 2. (35 N+11 K)IngredientsQuantity (Kg) required to produce one metric ton productUrea760 KgPotassium chloride329Binder15 kgSurfactant1Kg

[0050] Example 3. (25 N+21 K)IngredientsQuantity (Kg) required to produce one metric ton productUrea545 KgPotassium chloride428Binder25 kgSurfactant2 Kg

Claims

A pastille fertilizer composition, comprising:Urea in an amount of 25% to 75% by weight, preferably 50% to 70% by weight, and more preferably 60% to 70% by weight;A potassium chloride-containing material in an amount of 10% to 50% by weight, preferably 20% to 40% by weight, and more preferably 15% to 30% by weight;A binder in an amount of 0.5% to 5% by weight, preferably 0.5% to 2% by weight, and more preferably 1% to 2% by weight;A surfactant in an amount of 0.2% to 4% by weight, preferably 0.2% to 2% by weight, and more preferably 0.5% to 1% by weight; andOptionally, agriculturally relevant additives in an amount of 1% to 10% by weight, preferably 2% to 6% by weight, and more preferably 5% to 10% by weight,wherein the composition provides a homogeneous distribution of nutrients in a composite matrix and is suitable for controlled nutrient release.A process for producing a pastille fertilizer composition, comprising:Moten urea in an amount of 25% to 75% by weight, preferably 50% to 70% by weight, and more preferably 60% to 70% by weight, at a temperature of 130°C to 140°C to form molten urea;Transferring the molten urea to a mixing tank and adding a potassium chloride-containing material in an amount of 10% to 50% by weight, preferably 20% to 40% by weight, and more preferably 15% to 30% by weight, while maintaining a temperature of 100°C to 150°C, and stirring the mixture at 40 RPM for 0.1 to 2 hours to form a urea-potassium chloride molten mix;Adding a binder in an amount of 0.5% to 5% by weight, preferably 0.5% to 2% by weight, and more preferably 1% to 2% by weight, to the urea-potassium chloride molten mix, stirring the mixture at 40 to 300 RPM for 0.1 to 1 hour at a temperature of 100°C to 150°C, to form a urea-potassium chloride-binder mix;Adding a surfactant in an amount of 0.2% to 4% by weight, preferably 0.2% to 2% by weight, and more preferably 0.5% to 1% by weight, to the urea-potassium chloride-binder mix, stirring the mixture at 40 to 300 RPM for 0.1 to 1 hour at a temperature of 100°C to 150°C, to form a urea-potassium chloride-binder-surfactant mix;Optionally, adding agriculturally relevant additives in an amount of 1% to 10% by weight, preferably 2% to 6% by weight, and more preferably 5% to 10% by weight, to the urea-potassium chloride-binder-surfactant mix, and stirring the mixture under the same conditions to form a urea-potassium chloride-binder-surfactant-additives mix;Forming pastille fertilizer compositions from the urea-potassium chloride-binder-surfactant-additives mix using a roto-form pastillator; andCoating the pastille fertilizer composition with a formulation or agriculturally relevant materials in an amount of 0.1% to 10% by weight, preferably 3% to 8% by weight, and more preferably 1% to 5% by weight.The fertilizer pastille composition of claim 1, further comprising: a coating layer composed of inorganic or organic materials, selected from metal chalcogenides, silicates, long-chain nonpolar lipids, or combinations agriculturally relevant additives thereof, wherein the coating reduces hygroscopicity, improves mechanical strength, and enables controlled or sustained nutrient release.The fertilizer pastille composition of claim 1, wherein the agriculturally relevant additives are selected from plant growth regulators, hydrogels, nutrients, or pesticides.The fertilizer pastille composition of claim 1, wherein the potassium chloride-containing material is sourced from natural or synthetic sources.The fertilizer pastille composition of claim 1, wherein the composite matrix ensures compatibility with various halide materials, enabling customization for specific crop needs.The fertilizer pastille composition of claim 1, wherein the pastilles are reduced -hygroscopic nature and demonstrate improved shelf-life due to the incorporation of surfactants and coatings.The process of claim 2, wherein the temperature during the coating step is maintained below 100°C, ensuring preservation of the coating material's properties.The process of claim 2, wherein the roto-form pastillator forms pastilles of uniform size and shape, ensuring uniform nutrient release.The fertilizer pastille composition of claim 3, wherein the coating for enhancing hydrophobicity, improving agronomic performance and storage stability.

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