Process for production of sulfur bentonite pastille fertilizer composition enriched with phosphorus using fine rock phosphate

Abstract

An enriched fertilizer composition of sulphur bentonite that enhances soil mobility of phosphorus consists of a fine rock phosphate material sized between 1 to 50 microns and molten elemental sulfur combined with sodium bentonite clay. The fertilizer composition, produced in pastille form, includes a high proportion of rock phosphate (15 to 21 weight percent), molten elemental sulfur (70 to75 weight percent), and bentonite clay (9 tol3 weight percent). The disclosed composition may facilitate the conversion of rock phosphate into a plant-available form through the oxidation of elemental sulfur.

Description

Process for production of sulfur bentonite pastille fertilizer composition enriched with phosphorus using fine rock phosphate

[0001] The invention relates to a process to produce a sulphur bentonite pastille fertilizer composition enriched with phosphorus using fine rock phosphate for agricultural use.

[0002] It is evident that combining rock phosphate with elemental sulphur can provide phosphorus to soil in a form that plants can utilize. In agriculture, it's common to use finely ground rock phosphate, especially in acidic soils, to supply phosphorus. To enhance phosphorous supply in neutral and high pH soils, elemental sulphur mixes with the rock phosphate and sublimate.

[0003] However, this approach of using rock phosphate and elemental sulphur has only been somewhat effective for improving phosphorus nutrition supply. With the introduction of phosphatic fertilizers (superphosphates, phosphoric acids, diammonium phosphate, and monoammonium phosphate, monopotassium phosphate, etc.), this fertilization approach has become less practical in modern agricultural practices. Nonetheless, these materials are all derived from rock phosphate, making it a significantly cheaper source of phosphate and can be employed to provide a steady and substantial supply of phosphorus.

[0004] In the present invention, the use of rock phosphate in a particular particle size range (1-50 micrometers) for the enrichment of sulphur bentonite fertilizer is a key feature, allowing the phosphate content to serve as a phosphorus source during the growing season and complement other phosphatic fertilizers.

[0005] The great advantage of the present composition is the elimination of processing steps typically involved in the production of phosphatic fertilizers, leading to an overall reduction in environmental and carbon footprints. Additionally, there is an increase in calcium supply in the soils with the current compositions.

[0006] The present disclosure pertains to a phosphorus-enriched sulfur bentonite composition in pastille form, which includes a significant proportion of rock phosphate within a specific particle size range of 1 to 50 micrometers, constituting 15 to 21 by weight percent. It also contains molten elemental sulfur at 70-75 by weight percent and bentonite clay at 9 to 13 weight percent. This composition may enhance the conversion of rock phosphate into a form of phosphorus that is readily available to plants through the oxidation of elemental sulfur.

[0007] The technical problem addressed by this invention lies in the difficulty of producing cost-effective, rock phosphate-enriched sulfur-bentonite pastille fertilizers through the roto form pastillation process, particularly when trying to increase the rock phosphate content in a way that enhances phosphorous nutrient availability.

[0008] The invention related to an improved process that enables the production of a rock phosphate-enriched sulfur-bentonite fertilizer in pastille form with a significant phosphorus content and an optimized balance of sulfur and bentonite clay. The invention aims to overcome the challenges of low rock phosphate content and difficulty in achieving uniform sulfur distribution, making the fertilizer cost-effective and suitable for agricultural use.

[0009] The invention solves the problem of improving phosphorus availability in soil by using rock phosphate in a specific particle size range, combined with elemental sulfur and bentonite clay, to create an environmentally friendly and efficient fertilizer composition that provides sulphur, phosphorus, and other nutrients to plants. The disclosed compositions enhance the conversion of rock phosphate into a form that is more readily available to plants through the oxidation of elemental sulfur, while avoiding the processing steps required for traditional phosphatic fertilizers.

[0010] is an infographic of the process for the production phosphorus-enriched sulfur bentonite pastille form composition for fertilizer use.

[0011] shows a representative image of the pastille form of product.

[0012] In one embodiment of the present invention, in the past, considerable research and effort have been dedicated to developing fertilizers that incorporate sulphur. This heightened focus stems from the growing global demand for sulphur-containing fertilizers, which have been associated with low crop yields in certain cases attributed to sulphur deficiencies in the soil. A lack of sulphur can severely impact both the yield and quality of crops.

[0013] In another embodiment, many fertilizers containing sulphur, especially those based on sulphur-bentonite, typically utilize elemental sulphur, which does not leach like sulphates. Instead, small particles of elemental sulphur are converted into sulphate by soil bacteria through oxidation during the growing season. This process results in a slower release of nutrients and reduces the likelihood of nutrient loss from the soil. Moreover, elemental sulphur can be advantageous for agriculture as it may act as a pesticide, enhance the efficacy of phosphorus and nitrogen, and lower the pH of alkaline soils.

[0014] In one embodiment, promoting fertilizers that contain elemental sulphur, such as sulphur-bentonite and their enriched formulations with significant amounts of phosphorus and nitrogen, is beneficial. Current methods exist for producing these enriched sulphur-bentonite fertilizers. For instance, one method (CN103980024A) outlines a process for creating a sulphur-based fertilizer composition with a low rock phosphate content. In this composition, rock phosphate is included in minimal amounts, specifically 5 percent by weight or less, with the content of ground phosphate rock ranging from approximately.25 to.5 weight percent.

[0015] In another embodiment, the process described in CN103980024A has a limitation: the low presence of rock phosphate in the fertilizer composition, at 5 percent by weight or less. This poses a technical challenge in producing a cost-effective rock phosphate-enriched sulphur-bentonite pastille fertilizer through a roto form pastillation approach for agricultural use. The molten elemental sulphur is utilized in fertilizer composition. In one embodiment of the present invention, the 99.9 percent pure elemental sulphur is sourced from natural origins.

[0016] In one embodiment, elemental sulphur is incorporated into the fertilizer composition at a concentration ranging from 70 to 75 weight percent, relative to the total weight of the fertilizer composition. Ideally, the elemental sulphur concentration is between 71 to 72 weight percent. The most uniform distribution of sulphur particles throughout the pastilles is achieved when the elemental sulphur content is maintained between 71 to 72 weight percent based on the total weight of the fertilizer composition.

[0017] In another embodiment, the rock phosphate material, all naturally available or process grades employed in the composition and process of the present invention is preferably based on the rock phosphate. Additionally, at least one clay material, with sodium bentonite being the preferred choice, is required by this invention. The bentonite clay is included in an amount ranging from 9 to 13 weight percent based on the total weight of the fertilizer composition.

[0018] In another embodiment, further ingredients may be added to the fertilizer composition of the present invention to customize it for its intended end-use. Examples include micronutrients such as boron, selenium, zinc, manganese, iron, copper, molybdenum, cobalt, and their combinations. These nutrients can be supplied in elemental form or as salts. This approach results in enriched compositions with plant micronutrients. The quantity of plant micronutrients varies based on the type of fertilizer required, typically falling between 0.1 to 1.5 weight percent of the total composition.

[0019] In another embodiment, an example of producing a rock phosphate-enriched sulphur bentonite composition, or other micronutrient-enriched formulations, involves mixing molten sulphur, bentonite, and fine rock phosphate materials in a mixing tank or pit. In this embodiment of the present invention, a suspension of molten sulphur, bentonite clay, and rock phosphate is typically created through mixing.

[0020] In another embodiment, to prevent excess moisture introduction, bentonite powder and rock phosphate are stored in dry conditions. Ideally, the moisture content in the mixture is kept as low as possible, preferably ranging from 0.3 to 1 weight percent based on the total weight of the mixture, and more preferably from 0.4 to 0.7 weight percent.

[0021] In another embodiment, the proportions of molten sulphur and bentonite are adjusted to produce a pumpable slurry suitable for roto form pastillation and to achieve the desired final product composition. To produce a rock phosphate-enriched sulphur bentonite composition, the typical ratio of molten sulphur, bentonite, to rock phosphate is approximately 70:10:20 weight percent.

[0022] In another embodiment, mixing generally occurs at atmospheric pressure and within a temperature range of 130°C to 140°C. The present invention, the molten slurry comprises sulphur, bentonite clay, and fine rock phosphate. In this scenario, the bentonite clay and rock phosphate particles are typically dispersed or suspended within the slurry. Preferably, the rock phosphate particles have an average particle size of 50 microns.

[0023] In one embodiment, it is preferred that the molten sulphur slurry contains dispersed rock phosphate particles mixed with bentonite clay. This type of slurry, hereafter referred to as molten sulphur bentonite slurry, includes both dispersed bentonite clay and rock phosphate particles within a molten sulphur medium.

[0024] In one embodiment, the rock phosphate particles are effectively maintained in dispersion through the addition of bentonite and / or a viscosity modifier, resulting in a pumpable slurry. The optimal material balance and particle size of rock phosphate in the disclosed composition are crucial innovative elements central to this invention. One advantage of utilizing fine rock phosphate is its more homogeneous distribution throughout the molten sulphur-bentonite medium.

[0025] In a preferred embodiment of the present invention, the liquid phase consists of molten sulphur, and the direct use of molten sulphur in the disclosed process eliminates the need for extra steps, such as remelting sulphur. When incorporating elemental sulphur in its molten state, the temperature of the sulphur-containing mixture is ideally maintained between 135°C to 140°C.

[0026] In another embodiment, bentonite clay is suitable for mixing with the sulphur in a liquid molten phase and / or the fine rock phosphate material. The bentonite clay is added to the sulphur in the liquid phase before contact with the fine rock phosphate material occurs. The heated mixture is then pumped and distributed onto a roto form pastillation to produce fertilizer.

[0027] In one embodiment, the pastilles of the rock phosphate-enriched sulphur-bentonite composition obtained after the pastillation step do not require drying. In a preferred embodiment, the pastilles are air-exposed in the bagging unit, thus avoiding the need for additional equipment. An ideal size range for the pastilles is between 1 to 5. mm, with a preferred range of 2 to 4 mm. The production process consists of one or more of the steps outlined below.

[0028] In another embodiment, in the first step, molten sulphur at 99.9 percent purity is procured directly from an oil producer company and transferred into a pit or tank, adhering to the specified quantity of 70 to 75 weight percent.

[0029] In another embodiment, in the second step, the temperature of the molten sulphur in the pit or tank is maintained at 130 to140 °C. Sodium bentonite clay, comprising 9 to 13 weight percent, is then mixed with the molten sulphur obtained in the first step. This results in a sulphur-bentonite mix, which is mixed for 2 to 6 hours under conditions (40 RPM and 135 °C) that promote the dispersion of the clay within the molten sulphur medium, leading to the formation of a sulphur-bentonite mix.

[0030] In another embodiment, in the third step, rock phosphate material, with an average particle size of 50 microns and comprising 15 to 21 weight percent, is added to the sulphur-bentonite mix created in the second step. This mixture is further mixed for 4 to 8 hours under conditions (40 RPM and 135 °C) that facilitates the dispersion of rock phosphate particles into the molten sulphur-bentonite medium, resulting in the formation of a sulphur-bentonite-rock phosphate mix.

[0031] In another embodiment, in the fourth step, the sulphur-bentonite-rock phosphate mix generated in the third step is then pumped and distributed onto a roto form pastillator to produce fertilizer of the specified composition and specifications.

[0032] An enhanced pastille form of fertilizer sulphur-bentonite composition variants includes a significant amount of fine rock phosphate, in line with the disclosed inventive process, the exemplary compositions are as follows:Examples

[0033] Example 1. (0-4-0+70S)IngredientsQuantity (Kg) required to produce one metric ton productElemental sulphur (99.9 pure in molten form)700 KgSodium bentonite clay137 KgFine rock phosphate (26 percent P2O5 )153 Kg

[0034] Example 2. (0-5-0+70S)IngredientsQuantity (Kg) required to produce one metric ton productElemental sulphur (99.9 pure in molten form)700 KgSodium bentonite clay98 KgFine rock phosphate (26 percent P2O5)192 Kg

[0035] Example 3. (0-6-0+70S)IngredientsQuantity (Kg) required to produce one metric ton productElemental sulphur (99.9 pure in molten form)700 KgSodium bentonite clay100 KgFine rock phosphate (30 percent P2O5)200 Kg

Claims

An enriched pastille form of fertilizer sulphur bentonite composition includes a substantial amount of fine rock phosphate, which enhances the soil mobility of phosphorus for agricultural use and comprises the following steps.In the first step, molten sulphur at 99.9 percent purity is procured directly from an oil producer company and transferred into a pit or tank, adhering to the specified quantity of 70 to 75 weight percent.In the second step, the temperature of the molten sulphur in the pit or tank is maintained at 130 to 140 °C. Sodium bentonite clay, comprising 9 to 13 weight percent, is then mixed with the molten sulphur obtained in the first step. This results in a sulphur-bentonite mix, which is mixed for 2 to 6 hours under conditions (40 RPM and 135 °C) that promote the dispersion of the clay within the molten sulphur medium, leading to the formation of a sulphur-bentonite mix.In the third step, rock phosphate material, with an average particle size of 50 microns and comprising 15 to 21 weight percent, is added to the sulphur-bentonite mix created in the second step. This mixture is further mixed for 4 to 8 hours under conditions (40 RPM and 135 °C) that facilitates the dispersion of rock phosphate particles into the molten sulphur-bentonite medium, resulting in the formation of a sulphur-bentonite-rock phosphate mix.In the fourth step, the sulphur-bentonite-rock phosphate mix generated in the third step is then pumped and distributed onto a roto form pastillation to produce fertilizer of the specified composition and specifications.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1, wherein fine rock phosphate is present in an amount ranging from 15 to 22 percent by weight.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1, wherein the particle size of fine rock phosphate is between 1 to 50 microns.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1, wherein molten sulphur at 99.9 percent is present at 70 to 75 weight percent.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1, wherein sodium bentonite clay comprises 9 to 13 weight percent.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1, wherein the sulphur-bentonite-rock phosphate ratio is 70:10:20 by weight percent, pastillated at a temperature of 135°C on the roto form to produce fertilizer of the specified composition and specifications.An enriched pastille form of fertilizer sulphur bentonite composition with phosphorus according to claim 1 is intended for agricultural use.

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