METHODS FOR PRODUCING UREA CALCIUM SULFATE FROM MOIST PHOSPHOGYPSUM

Abstract

Method for producing a urea calcium sulfate (UCS) adduct is disclosed. The method for producing the UCS adduct, includes contacting urea with a moist phosphogypsum containing 10 wt. % to 30 wt. % of moisture, under conditions sufficient to form a slurry comprising formed UCS adduct.

Claims

1. A method for producing a urea calcium sulfate (UCS) adduct, the method comprising: (a) contacting urea with a moist phosphogypsum comprising 10 wt. % to 30 wt. % of moisture, under conditions sufficient to form a slurry comprising formed UCS adduct.

2. The method of claim 1, wherein an aqueous urea solution is contacted with the moist phosphogypsum to form the slurry.

3. The method of claim 2, wherein the formed slurry comprising formed UCS adduct comprises 10 wt. % to 30 wt. % of water.

4. The method of claim 1, wherein urea particles having a size of 0.1 mm to 1 mm are contacted with the moist phosphogypsum to form the slurry.

5. The method of claim 1, wherein urea granules and/or prills having a size of 1 mm to 4 mm are contacted with the moist phosphogypsum to form the slurry.

6. The method of claim 1, wherein the contacting conditions in step (a) include a temperature of 40° C. to 80° C.

7. The method of claim 1, wherein the moist phosphogypsum contacting the urea has a temperature of 30° C. to 60° C.

8. The method of claim 1, further comprising obtaining the moist phosphogypsum from a phosphoric acid manufacturing plant prior to step (a).

9. The method of claim 8, wherein: i) the moist phosphogypsum produced from the phosphoric acid manufacturing plant is not dried and/or pretreated to reduce moisture content of moist phosphogypsum below 10 wt. % prior to contacting the urea in step (a) and/or ii) wherein no water is added to the moist phosphogypsum produced from the phosphoric acid manufacturing plant after production of the phosphogypsum or in the contacting step (a) other than the water contained in the moist phosphogypsum from the phosphoric acid manufacturing plant.

10. The method of claim 8, wherein the moist phosphogypsum produced from the phosphoric acid manufacturing plant is not cooled to a temperature below 30° C. prior to contacting the urea in step (a).

11. The method of claim 1, wherein a molar ratio of urea contacting the moist phosphogypsum to calcium sulfate contained in the moist phosphogypsum contacted in step (a) is 1:0.25 to 1.2:0.16.

12. The method of claim 1, further comprising: (b) drying the slurry to form a dried fertilizer composition comprising the formed UCS adduct.

13. The method of claim 12, wherein the dried fertilizer composition comprises 0 wt. % to 10 wt. % of moisture.

14. The method of claim 12, wherein the drying in step (b) comprises contacting the slurry or a dryer used for drying the slurry with steam.

15. The method of claim 12, wherein 40 wt. % to 95 wt. % of the dried fertilizer composition is comprised of the formed UCS adduct.

16. The method of claim 1, further comprising granulating the formed UCS adduct before, during, and/or after drying the slurry.

17. The method of claim 16, wherein the granulating is performed in a granulator and step (a) is performed in a vessel different from the granulator.

18. The method of claim 17, wherein the granulating comprises contacting the formed UCS with steam or the granulator used for granulating the formed UCS with steam.

19. The method of claim 1, wherein the slurry of step (a) further comprises a base and/or a urease inhibitor.

20. The method of claim 1, wherein the method further comprises combining the formed UCS adduct with at least one additional fertilizer to form a fertilizer blend and/or compounded fertilizer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0060] FIGS. 1A-1C are: FIG. 1A a schematic of a system according to one embodiment of the present invention to produce UCS fertilizer granules from urea and moist phosphogypsum; FIG. 1B a schematic of a system according to another embodiment of the present invention to produce UCS fertilizer granules from urea and moist phosphogypsum where, the moist phosphogypsum is freshly obtained from a phosphoric acid production plant; FIG. 1C a schematic of a system according to another embodiment of the present invention to produce UCS fertilizer granules from urea and moist phosphogypsum where the moist phosphogypsum is freshly obtained from a phosphoric acid production plant and an optional storage of the produced UCS step is included before granulation.

[0061] FIG. 2: A UCS fertilizer granule containing at least 80 wt. % UCS produced according to one method of the present invention from urea and moist phosphogypsum. The dark grey area on the granule shows unreacted urea, the white area on the granule shows unreacted gypsum and the light grey area on the granule shows UCS adduct.

[0062] FIG. 3: A UCS fertilizer granule containing 30 to 40 wt. % UCS adduct. The dark grey area on the granule shows unreacted urea, the white area on the granule shows unreacted gypsum and the light grey area on the granule shows UCS adduct.

[0063] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0064] A process for producing a UCS fertilizer granule is disclosed. The UCS fertilizer granule can be produced from moist phosphogypsum. In some aspects, an UCS adduct can be formed from urea and freshly produced moist phosphogypsum from phosphoric acid manufacturing. In some aspects, the formed UCS adduct can be granulated to form UCS fertilizer granules.

[0065] The process of the current invention can provide for an economic method to produce a stable and high quality UCS adduct from moist phosphogypsum.

[0066] The UCS adduct of the present invention can be produced by the following non-limiting reaction:

CaSO.sub.4.Math.2H.sub.2O+4CO(NH.sub.2).sub.2.fwdarw.CaSO.sub.4.Math.4CO(NH.sub.2).sub.2+2H.sub.2O  (1)

[0067] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Process to Produce UCS Fertilizer Granules from Moist Phosphogypsum

[0068] The UCS adduct and UCS granules of the present invention can be made using a system such as, but not limited to, systems 100, 200, and/or 300 shown in FIG. 1A, FIG. 1B, or FIG. 1C, respectively, or a combination thereof. The systems can be continuous processes or batch processes capable of handling slurries. Referring to FIG. 1A, FIG. 1B, or FIG. 1C, the systems 100, 200, and/or 300 can include a urea phosphogypsum mixing vessel 102. Urea 110 and moist phosphogypsum 112 can be fed to the vessel 102. In some aspects, urea in form of an urea solution can be fed to the vessel 102. In some aspects, the urea solution can contain 10 wt. % to 30 wt. % or at least one of, equal to any one of, or between any two of 10, 15, 20, 25 and 30 wt. % of water. In some aspects, urea in form of urea particles having a size of 0.1 mm to 1 mm or at least one of, equal to any one of, or between any two of 0.1, 0.2, 0.4, 0.6, 0.8 and 1 mm can be fed to the vessel 102. In some aspects, urea in form of urea granules and/or prills having a size of 1 mm to 4 mm or at least one of, equal to any one of, or between any two of 1, 2, 3 and 4 mm can be fed to the vessel 102. The moist phosphogypsum 112 fed to the vessel 102 can contain i) 10 wt. % to 30 wt. % or 15 wt. % to 30 wt. % or at least one of, equal to any one of, or between any two of 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30 wt. % of water e.g. moisture and ii) 65 wt. % to 88 wt. % or at least one of, equal to any one of, or between any two of 65, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, and 88 wt. % of calcium sulfate. In some aspects, the phosphogypsum can further contain one or both of P.sub.2O.sub.5 and/or phosphoric acid with total amount of 0.5 wt. % to 5 wt. % or at least one of, equal to any one of, or between any two of 0.5, 1, 2, 3, 4, and 5 wt. %. The moist phosphogypsum 112 fed to the vessel 102 can have a temperature of 30° C. to 80° C. or 30° C. to 60° C. or 35° C. to 55° C. at least one of, equal to any one of, or between any two of 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80° C.

[0069] In some aspects, urea 110 and the moist phosphogypsum 112 can be fed to the vessel 102 separately. In some aspects, urea 110 and moist phosphogypsum 112 can be premixed (such as in a pre-mixing zone) before and can fed to the vessel as a combined feed (not shown). Optionally water 111 can be fed to the vessel 102. The optional water 111 can be different from water present in urea, such as moisture in the added urea particles, prills, or granules or water in the added urea solution, and water present in moist phosphogypsum, such as a moisture in the moist phosphogypsum. In some aspects, all or part of the optional water 111 can be premixed with the urea 110 and/or the moist phosphogypsum 112 and can be fed to the vessel as combined feed (not shown).

[0070] In the vessel 102, urea 110, moist phosphogypsum 112 and the optional water 111, can be combined to form a slurry containing a UCS adduct. In some aspects, the UCS adduct can be formed by the reaction 1. The water content of the slurry can be 10% to 50 wt. % or 10% to 30 wt. % or at least one of, equal to any one of, or between any two of 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, and 50 wt. %. In some aspects, the vessel 102 can be a continuous stirred-tank reactor. Mixing (e.g., agitator rpm of between 40 to 60 RPM) can be used to promote formation of the UCS adduct and/or to decrease the amount of heat required for the formation. The vessel 102 may include a rotatable section, a rotatable internal container, and/or a section that vibrates. In some instances, the rotatable section and/or rotatable internal container may contain internal flights and/or be rotated to induce movement of the reactants (urea 110 and moist phosphogypsum 112). In some aspects, molar ratio of the urea fed to the vessel 102 to calcium sulfate contained in the moist phosphogypsum fed to the vessel 102 can be 1:0.25 to 1.2:0.16 or at least one of, equal to any one of, or between any two of 1:0.25, 1.1:0.2, and 1.2:0.16.

[0071] Urea dissolution is an endothermic process. Optionally, the temperature of the vessel 102 can be increased to 1) increase the formation of the UCS adduct, 2) decrease the amount of water 111 needed, and/or 3) decrease the viscosity of the aqueous slurry. In some aspects, urea 110 and the moist phosphogypsum 112 can be contacted at 40° C. to 100° C. or 40° C. to 80° C. or at least one of, equal to any one of, or between any two of 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100° C. in the vessel 102 to form the slurry. Heat can be provided by any means suitable or known. In some instances, steam can be used. The optional use of steam can inhibit absorption of heat from the surroundings and hence lower the temperature requirement in the vessel 102 without additional energy. With steam injection, the urea can be rapidly dissolved while the surrounding material is maintained at the high temperature, which can preferably be about 40° C. to 100° C. or 60° C. to 100° C. or 40° C. to 80° C. or any range or value therein. Additional active or inactive ingredients can be added to the slurry while in the vessel 102 or at any other time.

[0072] In some aspects, the slurry 113 containing UCS can exit the vessel 102 and enter an optional second mixing and stabilizing zone where additional UCS such as recycle UCS, additional urea, additional phosphogypsum, calcium sulfate, an additive or inactive ingredients, or any combination thereof can be added to the slurry 113 (not shown). The slurry 113 exiting the vessel 102 or the optional second mixing and stabilizing zone can typically contain more than 10 wt. % water. The slurry 113 can optionally contain a urease inhibitor and/or a base. In some aspects, the optional urease inhibitor and/or the base can added to the vessel 102 with a separate stream (not shown), and/or can be added with the urea 110, moist phosphogypsum 112, and/or the optional water 111 stream(s). In some aspects, the optional urease inhibitor and/or the base can added to the optional second mixing and stabilizing zone. The base can contain an oxide, carbonate, acetate, and/or hydroxide of a group 1 metal, group 2 metal, group 13 metal, and/or ammonium. In certain aspects, the base can contain CaO and/or MgO. In certain particular aspects, the base can be MgO. In certain aspects, the base such as MgO can be comprised in particulate solids. In certain aspects, the particulate solids can have an average diameter of 0.1 μm to 150 μm or 1 μm to 50 μm. In certain aspects, the urease inhibitor can contain a thiophosphoric triamide derivative or phenyl phosphorodiamidate (PPDA). In certain aspects, the thiophosphoric triamide derivative can be N-(n-butyl) thiophosphoric triamide (NBPT).

[0073] The slurry 113 from the vessel 102, or the optional second mixing and stabilizing zone if used, can be fed to a dryer 103. In the dryer 103, the slurry can be dried to form a dried fertilizer composition containing the formed UCS adduct. The dryer 103 can be a part or function of the vessel 102 (not shown) or can be separate. Heat for drying can be provided by any means suitable or known. In some embodiments, the dryer 103 can be heated by steam (not shown), such as in steam jacketed dryer. The dried fertilizer composition 114 exiting the dryer 103 can contain 0 wt. % to 10 wt. %, or 0 wt. % to 2 wt. %, or 2 wt. % to 10 wt. % or at least one of, equal to any one of, or between any two of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 wt. % of moisture. The slurry can be dried in the dryer at a temperature 35° C. to 100° C. or at least one of, equal to any one of, or between any two of 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C. and 100° C. to form the dried fertilizer composition.

[0074] The dried fertilizer composition 114 formed in the dryer 103 can be granulated in a granulator 104 to form a granulated fertilizer composition 115 containing the formed UCS adduct. The granulated fertilizer composition 115 can contain UCS fertilizer granules containing the formed UCS adduct. In some aspects, the granulator 104 can be separate from the vessel 102 and the dryer 103. In some aspects, the vessel 102, the dryer 103 and the granulator 104 can be the same vessel or part of a same vessel. The granulator 104, may include a rotatable section, a rotatable internal container, and/or a section that vibrates. In some instances, the rotatable section and/or rotatable internal container may contain internal flights and/or be rotated to induce movement of the dried fertilizer composition 114 in the granulator 104. The granulator 104 can be or can be part of a granulation drum, pugmill, pan granulator, etc. In some aspects, 40 wt. % to 95 wt. % or 55 wt. % to 95 wt. % or at least one of, equal to any one of, or between any two 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 and 95 wt. % of the dried fertilizer composition 114 and/or the granulated fertilizer composition 115 can be comprised of the UCS adduct. The granulated fertilizer composition 115 can optionally contain 0.2 wt. % to 7 wt. % or at least any one of, equal to any one of, or between any two of 0.2 wt. %, 0.5 wt. %, 1 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, 6 wt. %, 7 wt. % of a base, such as MgO. The granulated fertilizer composition 115 can optionally contain 0.01 wt. % to 0.2 wt. % or at least any one of, equal to any one of, or between any two of 0.01 wt. %, 0.05 wt. %, 0.1 wt. %, 0.15 wt. % and 0.2 wt. % of a urease inhibitor, such as NBPT. In some aspects, granulated fertilizer composition 115 can contain NBPT and MgO at a weight ratio of 0.03:1 to 0.06:3 or at least any one of, equal to any one of, or between any two of 0.03:1, 0.06:1, 0.06:1.5, 0.06:2, 0.06:2.5, and 0.06:3.

[0075] Optionally, water or an aqueous solution, such as steam and/or a scrubber solution, can be combined with the dried fertilizer composition 114 in the granulator 104 to facilitate granulation of the dried fertilizer composition 114 (not shown). Optionally additional UCS such as recycled UCS, additional urea, additional phosphogypsum, calcium sulfate or one or more additives or any combination thereof can be added to the material in the granulator 104 (not shown).

[0076] Optionally the granulated fertilizer composition can be further dried after granulation (not shown). The further drying can occur in a further drying zone that can be a dryer and/or part of or a function of the granulator 104 or the vessel 102. In some aspects, the dried fertilizer composition 114 can granulated and further dried at the same time, such as in a rotating dryer.

[0077] Optionally the UCS fertilizer and/or UCS fertilizer granules can be coated with one or more coating material to form coated UCS fertilizer granules.

[0078] Referring to FIG. 1B and FIG. 1C, in some embodiments, the moist phosphogypsum 112 can be obtained from a phosphoric acid production system 116. The phosphoric acid production system 116 can produce the moist phosphogypsum 112 and phosphoric acid (not shown) from rock phosphate (not shown). In some aspects, the moist phosphogypsum 112, can be a freshly produced moist phosphogypsum from the phosphoric acid production system 116. As used herein “freshly produced moist phosphogypsum” can refer to phosphogypsum produced from the phosphoric acid production system that has not been dried to reduce the moisture content below 10 wt. % and/or cooled to reduce the temperature below 30° C., prior to contacting the phosphogypsum with urea. The freshly produced moist phosphogypsum can have a moisture content of 10 wt. % to 30 wt. % or 15 wt. % to 30 wt. %, a temperature of 30° C. to 80° C. or 30° C. to 60° C. or 35° C. to 55° C. and pH (of 10 wt. % aqueous solution) of 1.5 to 4 or 2 to 3. In some aspects, the freshly produced moist phosphogypsum can have a moisture content of 15 wt. % to 30 wt. %, a temperature of 35° C. to 55° C. and pH (of 10 wt. % aqueous solution) of 2 to 3. The pH of the freshly produced moist phosphogypsum can be measured in a 10 wt. % of aqueous solution, e.g., 10 gm of moist phosphogypsum in 100 gm of solution.

[0079] Optionally, the dried UCS fertilizer composition 114 can be stored before granulation (FIG. 1C). During storage, in some instances, the dried fertilizer composition 114 is not continuously mixed or actively heated to temperatures above ambient temperature (e.g., the dried fertilizer composition 114 can sit in a container located in a storage facility). The dried fertilizer composition 114 can be stored in a storage container 118. The storage container 118 can be part of the vessel 102 (not shown) or can be part of the dryer 103 (not shown) and/or part of the granulator 104, or can be separate from the first vessel 102, dryer 103, or granulator 104. In some aspects, storage container 118 can be a part of the vessel 102, the dryer 103, or granulator 104 while these are not mixing or actively heating (not shown). In some aspects, if stored, the dried fertilizer composition 114 after storage can be fed to the granulator 104 to form the granulated fertilizer composition 115 containing the formed UCS adduct.

[0080] In some embodiments, additional UCS such as recycle UCS, additional urea, additional phosphogypsum, calcium sulfate, or an additive can be added to a one or more process steps to help maintain consistency of the mixture, or provide beneficial properties to the slurry, dried UCS fertilizer composition, and/or UCS fertilizer granule.

B. UCS Fertilizer Granules

[0081] The UCS fertilizer granule produced can, in some instances, contain low amounts of moisture. The free-moisture content of the granule can be less than 0.6 wt. %, less than 0.5 wt. % water or 0.25 wt. % to less than 0.6 wt. % water. In some instances, the free moisture content is 0.5, 0.4, 0.3, 0.2, 0.1, or 0 wt. %.

[0082] The granule can be comprised of one or more particles. In some aspects, a first portion of the particles can be the UCS adduct. In certain non-limiting aspects, the first portion of the particles can have an average particle size of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, or 900 micrometers or any size there between. In some embodiments, the particles can be elongated particles or can be substantially spherical particles or other shapes, or combinations of such shapes. Non-limiting examples of shapes include a sphere, a puck, an oval, a rod, an oblong, or a random shape. In some aspects, 40 wt. % to 95 wt. % or 55 wt. % to 95 wt. % or at least one of, equal to any one of, or between any two 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 and 95 wt. % of the UCS granules can be comprised of the UCS adduct.

[0083] The UCS granules can have a crush strength of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 kgf/granule, or more, or any amount there between, preferably 2 kgf/granule to 5 kgf/granule.

[0084] The UCS granules and/or UCS fertilizers can in some instances contain a coating on the surface of the UCS granule and/or UCS fertilizers. In some instances, the coating can include nutrients for a plant, inhibitors of urea hydrolysis and/or nitrification, agents to slow or increase the rate of degradation of the granule and/or fertilizers, agents to repel moisture and/or provide a hydrophobic layer, agents that decrease or increase the reactivity of the granule and/or fertilizers, agents that provide additional benefits to plants, agents that increase the stability and/or crush strength of the granule and/or fertilizers, pH buffering agents, drying agents, etc. or any combination thereof. The coating can be a commercially available coating, an oil, a fertilizer, a micronutrient, talc, a seaweed and/or seaweed extract, a wax, etc. In some instances, the coating can contain surfactants. In some instances, the coating contains a wax, surfactants, and/or an amine-based compound.

C. Blended or Compounded Fertilizer Compositions

[0085] The UCS adduct and/or the UCS fertilizer granules of the present invention can also be included in a blended or compounded fertilizer composition comprising other fertilizers, such as other fertilizer granules. Additional fertilizers can be chosen based on the particular needs of certain types of soil, climate, or other growing conditions to maximize the efficacy of the UCS in enhancing plant growth and crop yield. The other fertilizer granules can be granules of urea, single super phosphate (SSP), triple super phosphate (TSP), ammonium sulfate, monoammonium phosphate (MAP), diammonium phosphate (DAP), muriate of potash (MOP), and/or sulfate of potash (SOP), and the like.

[0086] The UCS adduct and/or UCS granules can be used alone or in combination with other fertilizer actives and micronutrients. In some aspects, the other fertilizer actives and micronutrients can be added with any of the ingredients at the beginning of the drying stage or granulation process or at any later stage.

[0087] Non-limiting examples of additional additives can be micronutrients, primary nutrients, and secondary nutrients. A micronutrient is a botanically acceptable form of an inorganic or organometallic compound such as boron, copper, iron, chloride, manganese, molybdenum, nickel, or zinc. A primary nutrient is a material that can deliver nitrogen, phosphorous, and/or potassium to a plant. Nitrogen-containing primary nutrients may include urea, ammonium nitrate, ammonium sulfate, diammonium phosphate, monoammonium phosphate, urea-formaldehyde, or combinations thereof. A secondary nutrient is a substance that can deliver calcium, magnesium, and/or sulfur to a plant. Secondary nutrients may include lime, gypsum, superphosphate, or a combination thereof. For example, in some instances the UCS granule can contain calcium sulfate, potassium sulfate, magnesium sulfate or a combination thereof.

[0088] In one aspect, the UCS adduct containing fertilizer compositions, and/or UCS granules can comprise one or more inhibitors. The inhibitor can be a urease inhibitor or a nitrification inhibitor, or a combination thereof. In one aspect, a urease inhibitor and a nitrification inhibitor are included. In one aspect, the inhibitor can be a urease inhibitor. Suitable urease inhibitors include, but are not limited to, N-(n-butyl) thiophosphoric triamide (NBTPT) and phenylphosphorodiamidate (PPDA). In one aspect, the UCS fertilizer granule and/or UCS fertilizer can comprise NBTPT or PPDA, or a combination thereof. In another aspect, the inhibitor can be a nitrification inhibitor. Suitable nitrification inhibitors include, but are not limited to, 3,4-dimethylpyrazole phosphate (DMPP), dicyandiamide (DCD), thiourea (TU), 2-chloro-6-(trichloromethyl)-pyridine (Nitrapyrin), 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazol, which is sold under the tradename Terrazole®, by OHP Inc., USA, 2-amino 4-chloro 6-methyl pyrimidine (AM), 2-mercaptobenzothiazole (MBT), or 2-sulfanilamidothiazole (ST), and any combination thereof. In one aspect, a nitrification inhibitor can comprise DMPP, DCD, TU, nitrapyrin, 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazol, AM, MBT, or ST, or a combination thereof. In one aspect, the UCS fertilizer granule and/or UCS fertilizer can comprise NBTPT, DMPP, TU, DCD, PPDA, nitrapyrin, 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazol, AM, MBT, or ST, or a combination thereof.

D. Method of Using the UCS Fertilizer Granules

[0089] The UCS adduct and/or UCS fertilizer granules of the present invention can be used in methods of increasing the amount of nitrogen in soil and of enhancing plant growth. Such methods can include applying to the soil an effective amount of a composition comprising the UCS adduct and/or UCS fertilizer granule of the present invention. The method may include increasing the growth and yield of crops, trees, ornamentals, etc. such as, for example, palm, coconut, rice, wheat, corn, barley, oats, and soybeans. The method can include applying the UCS adduct and/or UCS fertilizer granules of the present invention to at least one of a soil, an organism, a liquid carrier, a liquid solvent, etc.

[0090] Non-limiting examples of plants that can benefit from the fertilizer of the present invention include vines, trees, shrubs, stalked plants, ferns, etc. The plants may include orchard crops, vines, ornamental plants, food crops, timber, and harvested plants. The plants may include Gymnosperms, Angiosperms, and/or Pteridophytes. The Gymnosperms may include plants from the Araucariaceae, Cupressaceae, Pinaceae, Podocarpaceae, Sciadopitaceae, Taxaceae, Cycadaceae, and Ginkgoaceae families. The Angiosperms may include plants from the Aceraceae, Agavaceae, Anacardiaceae, Annonaceae, Apocynaceae, Aquifoliaceae, Araliaceae, Arecaceae, Asphodelaceae, Asteraceae, Berberidaceae, Betulaceae, Bignoniaceae, Bombacaceae, Boraginaceae, Burseraceae, Buxaceae, Canellaceae, Cannabaceae, Capparidaceae, Caprifoliaceae, Caricaceae, Casuarinaceae, Celastraceae, Cercidiphyllaceae, Chrysobalanaceae, Clusiaceae, Combretaceae, Cornaceae, Cyrillaceae, Davidsoniaceae, Ebenaceae, Elaeagnaceae, Ericaceae, Euphorbiaceae, Fabaceae, Fagaceae, Grossulariaceae, Hamamelidaceae, Hippocastanaceae, Illiciaceae, Juglandaceae, Lauraceae, Lecythidaceae, Lythraceae, Magnoliaceae, Malpighiaceae, Malvaceae, Melastomataceae, Meliaceae, Moraceae, Moringaceae, Muntingiaceae, Myoporaceae, Myricaceae, Myrsinaceae, Myrtaceae, Nothofagaceae, Nyctaginaceae, Nyssaceae, Olacaceae, Oleaceae, Oxalidaceae, Pandanaceae, Papaveraceae, Phyllanthaceae, Pittosporaceae, Platanaceae, Poaceae, Polygonaceae, Proteaceae, Punicaceae, Rhamnaceae, Rhizophoraceae, Rosaceae, Rubiaceae, Rutaceae, Salicaceae, Sapindaceae, Sapotaceae, Simaroubaceae, Solanaceae, Staphyleaceae, Sterculiaceae, Strelitziaceae, Styracaceae, Surianaceae, Symplocaceae, Tamaricaceae, Theaceae, Theophrastaceae, Thymelaeaceae, Tiliaceae, Ulmaceae, Verbenaceae, and/or Vitaceae family.

[0091] The effectiveness of compositions comprising the UCS adduct and/or UCS fertilizer granules of the present invention can be ascertained by measuring the amount of nitrogen in the soil at various times after applying the fertilizer composition to the soil. It is understood that different soils have different characteristics, which can affect the stability of the nitrogen in the soil. The effectiveness of a fertilizer composition can also be directly compared to other fertilizer compositions by doing a side-by-side comparison in the same soil under the same conditions.

[0092] In one aspect, the UCS fertilizer granules and/or UCS fertilizer of the present invention can have a density that is greater than water. This can allow the granules and/or fertilizers to sink in water rather than float. This can be especially beneficial in instances where application is intended to a crop that is at least partially or fully submerged in water. A non-limiting example of such a crop is rice, as the ground in a rice paddy is typically submerged in water. Thus, application of UCS granules and/or UCS fertilizer to such crops can be performed such that the granules and/or fertilizer are homogenously distributed on the ground that is submerged under water. By comparison, granules and/or fertilizers that have a density that is less than water would have a tendency to remain in or on the water surface, which could result in washing away and/or coalescence of the granules and/or fertilizers, either of which would not achieve homogenous distribution of the granules and/or fertilizers to the ground that is submerged under water.

EXAMPLES

[0093] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results

Example 1

Producing UCS Adduct and UCS Granules from Moist Phosphogypsum

[0094] Moist phosphogypsum and urea can be mixed in a vessel to form a slurry containing UCS adduct. Moist phosphogypsum having a composition as shown in Table 1 can be used. pH of an aqueous solution containing 10 wt. % of the moist phosphogypsum is 2.4.

[0095] Urea in form of urea solution, granules, prills, and/or powder can be added to the vessel.

TABLE-US-00001 TABLE 1 Composition of moist phosphogypsum. Component wt. % Free Moisture 18.4 Total P.sub.2O.sub.5/Water soluble P.sub.2O.sub.5 1.43/0.87 CaSO.sub.4 77.62 SiO.sub.2 1.83 MgO 0.01 Fe.sub.2O.sub.3 0.01 F 0.32 Na.sub.2O 0.18 K.sub.2O 0.02 Cd 0.0001 Cr 0.0014 Pb 0.0002 Sr 0.08 Al.sub.2O.sub.3 0.08

[0096] The temperature of the urea phosphogypsum mixture and/or slurry can be kept around 60° C. The vessel can be rotated at a speed around 5-10 RPM to mix/convert the urea/phosphogypsum to the slurry containing UCS adduct. The moisture content of the slurry can be kept to around 20 wt. % to obtain a wet consistency. A residence time in the reaction vessel can be 30 minutes.

[0097] The slurry can be dried at a temperature about 75° C. to 95° C., such as 90° C. to form a dried fertilizer composition containing the UCS adduct. The UCS adduct content of the dried fertilizer composition can be above 80 wt. % and the water content of the dried fertilizer composition can be less than about 10 wt. % water but above 0.5 wt. % water. The dried fertilizer composition can be in a Run of Pile form (ungranulated).

[0098] The dried fertilizer composition can then be granulated in a granulator to obtain a granulated fertilizer composition containing UCS fertilizer granules. The fertilizer composition can further be dried during granulation to moisture content 0.5 wt. %. The UCS adduct content of the granulated fertilizer composition can be about 80 wt. %. FIG. 2 shows a UCS fertilizer granule containing greater than 80 wt. % UCS adduct. The UCS fertilizer granules are expected to be able to be produced in any size required for fertilizer applications, such as spherical granules having a diameter of 5 mm and 5 cm. It was found urea and calcium sulfate can be sufficiently separated in the granule with 60 wt. % or more of UCS adduct. When the urea and calcium sulfate are sufficiently separated in the granule, the granule can have a long term storage life. In some instances, sufficiently separated can be when a cross section of the UCS granule under microscope shows clear demarcation of the unreacted urea and calcium sulfate. In some instances, sufficiently separated can be when UCS adduct and unreacted urea and gypsum regions can be distinguished under a microscope with 80× magnification.

[0099] If the UCS product is found to have nutrient levels that are slightly off specification, then minor adjustments in nutrient content can be achieved by adding fresh urea/phosphogypsum/calcium sulfate as solid to the granulating UCS.

[0100] In this example, to produce 20 MT/hr of UCS slurry (20 wt. % water), 9.4 MT/hr of urea, 10.6 MT/hr of moist phosphogypsum can be used. The UCS fertilizer granule can have 27 wt. % nitrogen (N), 7 wt. % sulfur (S), and 9 wt. % calcium (Ca).

Example 2 (Comparative Example)

Producing UCS Adduct and UCS Granules from Dried Phosphogypsum

[0101] In a comparative example UCS fertilizer granules can be produced with a method similar to example 1, except phosphogypsum with moisture content 2-3 wt. % can be used instead of moist phosphogypsum and the moisture content of the slurry can be kept to around 2-3 wt. %. The composition of the phosphogypsum used for comparative Example 2 can be similar to Table 1, except free moisture content is 2-3 wt. %. The UCS adduct content of the granulated fertilizer composition produced in Example 2 was shown to be about 30 to less than 40 wt. %. FIG. 3 shows a UCS fertilizer granule containing 30 wt. % to less than 40 wt. % UCS. Urea and calcium sulfate are not sufficiently separated in the granule of Example 2, and the granule has less storage life compared to a granule of example 1.