SPRAY NOZZLE FOR THE PRODUCTION OF UREA-SULFUR FERTILIZER

Description

[0001] The invention relates to a spray nozzle for producing a urea-sulfur fertilizer, a fluidized bed granulator with a spray nozzle for producing a urea-sulfur fertilizer, a method for producing a urea-sulfur fertilizer and the use of the spray nozzle for producing fertilizer granules.

[0002] In view of global population growth, the development of flexible and efficient fertilizer mixtures is becoming increasingly important. Not only the fertilizer itself, i.e. its chemical composition, plays a role, but also its processing into transportable containers. The most important factor here is certainly granulation into uniform particles of the same size and consistency. Important parameters include low dust formation, strength, low tendency to aggregate, homogeneous size, storability, and durability. An established granulation technique is fluidized-bed granulation, which has improved particle properties compared to, for example, prilling techniques. An example of the production of urea-containing fertilizer granules using fluidized-bed granulation can be found in WO 2010 / 060535 A1, e.g., in paragraphs

[0025] -

[0035] .

[0003] The use of urea-sulfur fertilizers in agriculture has been known for some time. In such fertilizer mixtures, both nitrogen and sulfur can be provided to the plant simultaneously, thus eliminating the steps and costs associated with applying additional fertilizer. Sulfur can be present in both elemental and water-soluble forms, such as sulfate. The water-soluble sulfur form can be absorbed directly by the plant, while elemental sulfur must first be converted into the water-soluble form by microorganisms in the soil. This conversion process thus involves a kind of "depot effect," so that the sulfur is slowly released to the plant over a longer period of time. In this way, targeted and controlled sulfur release is possible, for example, through mixtures of sulfate and elemental sulfur.In combination with urea, for example, this enables the sown plants to be supplied with nitrogen via the urea in the early stages and with sulfur in the subsequent growth phases.

[0004] For this reason, urea-sulfur fertilizers with a homogeneous distribution of urea and sulfur are becoming increasingly important. Examples can be found, for example, in US Pat. No. 4,330,319 A.

[0005] To ensure good biodegradability of elemental sulfur in the soil, the smallest possible particles are necessary. These small particles, unlike larger particles, have a larger surface area relative to their volume. This larger surface area, particularly the larger specific surface area (determined, for example, using the BET method, e.g., according to DIN ISO 9277), improves the accessibility of elemental sulfur to soil microorganisms.

[0006] Since melts of elemental sulfur and urea are poorly miscible, particularly due to their different densities and viscosities, urea-sulfur fertilizers are often marketed in the form of sulfur-coated urea particles. Polymer-sulfur-coated urea particles, for example, are also possible. However, coating the urea particles with sulfur is a rather complex process, and the release rates of both sulfur and urea into the soil are difficult to predict and reproduce. Furthermore, coated urea particles can often have a significantly larger particle size, which, as described above, has a negative impact on the uniform decomposition of elemental sulfur. Studies (Effect of particle size on the oxidation of elemental sulfur); CC: Boswell et al.; New Zealand J.of Agricultural Res; 1988, 31, 179-186) have shown that particle sizes of 10 µm to 150 µm, especially 10 µm to 38 µm, are preferred.

[0007] Due to the aforementioned poor miscibility of urea and elemental sulfur, mixing devices such as mixers are often used. However, these require additional equipment components, such as static mixers. These additional process steps also inevitably increase the costs of the process. Another approach is mixing additives. These improve the miscibility of the components, for example, by reducing the surface tension of sulfur and urea in the melt.

[0008] At the same time, however, additional additives change the properties of the finished granules and increase the cost of the finished product.

[0009] US 3,100,698 A discloses a urea-sulfur fertilizer and its production from a urea and sulfur melt, mixing of the melts and obtaining the solid particles, for example via a prilling process.

[0010] WO 03 / 106376 A1 discloses a process for producing a urea-sulfur fertilizer in which an amphoteric additive, relative to the mixture of sulfur and urea, is added. Examples of suitable surfactants are C 6-30 fatty acids, preferably myristic acid.

[0011] WO 2014 / 005695 A1 discloses a process for producing an emulsion of elemental sulfur particles. Urea-sulfur fertilizers can be obtained by adding a multifunctional surfactant.

[0012] WO 2015 / 104296 A1 discloses a fertilizer composition comprising urea, sulfur and a lignin compound.

[0013] Further examples of a homogeneously distributed urea-sulfur fertilizer and processes for its production can be found in WO 2015 / 104286 A1 and WO2016 / 016150 A1.

[0014] WO 2005 / 061118 A1 discloses a spray nozzle for fluidized-bed granulation. This nozzle contains a mixture of the atomization medium with the melt in the nozzle.

[0015] WO 2017 / 005695 A1 discloses a process for producing a particulate fertilizer based on elemental sulfur and urea. The disclosed process does not require the use of additional additives to produce the sulfur / urea mixture.

[0016] JP 2003 103 203 A discloses a two-fluid spray nozzle having a first flow path for introducing the first fluid, a material in the liquid state, into a part opened at the head end and a second flow path for introducing a second fluid (compressed air) into the part opened at the head end.

[0017] The present invention has the object of providing a spray nozzle for producing an improved homogeneously distributed urea / sulfur fertilizer granulate, which allows a process to be carried out without additional mixing steps or additives, or reduces the use of further mixing steps or additives.

[0018] The object of the invention is surprisingly achieved by a spray nozzle according to claim 1. Further advantageous embodiments can be found in the dependent claims.

[0019] The invention further comprises a fluidized-bed granulator with a spray nozzle for producing urea fertilizer granules and / or urea-sulfur fertilizer granules, a method for producing a urea-sulfur fertilizer, and the use of the spray nozzle for producing fertilizer granules. Further advantageous embodiments can be found in the respective dependent claims.

[0020] The spray nozzle according to the invention for producing urea fertilizer granules and / or urea-sulfur fertilizer comprises at least one conveying channel and an atomization gas channel. The spray nozzle preferably contains or is constructed from metals and / or metal alloys, particularly preferably corrosion-resistant metals and / or metal alloys, especially preferably stainless steels. Suitable metals / metal alloys include, for example, iron, chromium, vanadium, nickel, titanium, aluminum, cobalt, and tungsten. The spray nozzle according to the invention can also contain temperature-resistant (> 100°C) polymers or ceramics. Optionally, the spray nozzle, particularly in the region of the conveying channel, can have corrosion-inhibiting coatings, for example, polytetrafluoroethylene. The spray nozzle is characterized in that the conveying channel has at least one separating pin and the atomization channel has at least one swirling element.

[0021] According to the invention, the separating pin is designed as a single, single, or multiple crossing web. The separating pin enables the melt to be separated at the separating pin in the direction of melt flow. The term "melt" within the meaning of the invention encompasses salt melts, salt and / or solid solutions, dispersions, and / or mixtures thereof. Preferably, the term "melt" within the meaning of the invention encompasses urea solutions, solutions / emulsions / dispersions with sulfur salts, and / or dispersions or solutions with elemental sulfur, preferably individually or in total with more than 50 wt.% urea, sulfur, and / or sulfur salts. In the direction of melt flow, the melt is recombined downstream of the separating pin. This separation and recombining of the melt enables better homogenization and mixing of the melt.The separating pin is preferably fixedly mounted in the conveyor channel; alternatively, a movable arrangement, for example, similar to a screw mounted in the conveyor channel, is also possible. The separating pin preferably comprises metals, metal alloys, glass blocks, ceramics, or temperature-stable (greater than 100°C to approximately 200°C) polymers.

[0022] The atomization channel has at least one swirling element and provides the gas flow, preferably an air flow, required to produce the atomized melt droplets or solution droplets. The term "atomization" in the context of the invention refers to fine melt or solution droplets dispersed in the gas flow. The term "atomized" in the context of the invention does not refer to the separation of molecular bonds or the presence of individual atoms. The swirling elements allow the atomization gas, for example, air, to be split into various secondary flows and turbulences. The swirling elements can be in the form of recesses, extensions, or elements mounted in the atomization channel.Swirling elements, within the meaning of the invention, comprise elements mounted or arranged in the atomization channel which deflect or divide the atomization gas and increase the turbulent portion of the atomization gas in the atomization channel. The swirling elements thus surprisingly enable sufficient formation of microdroplets of the melt. Surprisingly, a sulfur particle size of less than 30 µm was already achieved using the spray nozzle according to the invention without the need for further emulsifying additives in the urea / sulfur melt. The swirling elements can preferably be part of the atomization channel or incorporated elements comprising metals, metal alloys, glass blocks, ceramics, or polymers.Both the separating pin and the swirling elements surprisingly allow for a sulfur particle size of less than 30 µm in the finished urea-sulfur fertilizer granules, while distributing the sulfur particles homogeneously in the urea, for example, the urea matrix. The spray nozzle according to the invention also preferably allows for the elimination of additional stirring devices, such as mixers.

[0023] The intersecting separating pins enable very homogeneous mixing of the melt.

[0024] According to the invention, the swirling elements comprise solid elements. According to the invention, the conveying channel and the atomization gas channel form a common outlet opening, flush with each other. The mixing of the atomization gas and the melt droplets thus takes place outside the nozzle and not in a mixing chamber within the nozzle. This enables a very uniform and consistent mixing between the melt and the atomization gas.

[0025] The invention further comprises a fluidized-bed granulator comprising at least one spray nozzle according to the invention arranged on, at, and / or above a perforated plate. The spray nozzle according to the invention for producing a urea-sulfur fertilizer comprises at least one conveying channel and an atomization gas channel. The spray nozzle is characterized in that the conveying channel has at least one separating pin and the atomization channel has at least one swirling element. The spray nozzle and the preferred embodiments of the spray nozzle correspond to those described above. An exemplary structure of a fluidized-bed granulator, for example for producing urea-containing particles, can be found in WO 2010 / 060535 A1, e.g., in paragraphs

[0025] -

[0035] . Figure 1or US 4,701,353 A, DE 31 16 778A1 and US 4,219,589 A. The fluidized-bed granulator preferably has at least one granulator chamber, a perforated plate arranged in the granulator chamber, and spray nozzles according to the invention arranged in / on the perforated plate. The spray nozzles according to the invention are preferably connected to supply lines for a melt of urea and sulfur and to a supply line for the atomization gas. The term "atomization gas" in the sense of the invention refers to a gas for fluidizing, emulsifying, and dispersing the melt or solution, preferably of urea and sulfur. The fluidized bed in the granulator is connected to a fluidizing gas stream, preferably air. The seeds in the fluidized bed grow through contact with the melt droplets generated in the atomization medium.The finished particles are then cooled in the granulator or in a separate cooler and fed to further processes, such as screening, post-treatment and packaging.

[0026] The invention further comprises a process for producing a urea-sulfur fertilizer. The process according to the invention comprises at least the following steps: providing a melt containing urea and elemental sulfur, spraying the melt and atomization gas into a fluidized-bed granulator with a spray nozzle, and obtaining granules in the fluidized-bed granulator. If oxygen-sensitive granules are to be produced, gases / gas mixtures of noble gases, in particular argon, nitrogen, or carbon dioxide, can be used as the atomization gas instead of air or additionally. The spray nozzle used in the process is characterized in that the spray nozzle has at least one conveying channel and one atomization gas channel. Furthermore, the conveying channel has at least one separating pin, and the atomization channel has at least one swirling element.The spray nozzle and the preferred embodiments of the spray nozzle correspond to those described above.

[0027] In a preferred embodiment of the process, the spray nozzle is heated to a temperature range of 1°C to 10°C, preferably 2°C to 5°C, above the crystallization temperature of the melt. This temperature range allows for the melt to be dispensed with the appropriate viscosity and flow rate.

[0028] Preferably, the melt is introduced via the conveyor channel at a pressure of 0.5 bar to 7 bar. All pressure specifications used refer to the overpressure in bar above atmospheric pressure.

[0029] Preferably, the melt is introduced via the conveyor channel at a flow rate of 50 kg / h to 600 kg / h.

[0030] In a further preferred embodiment, the atomization gas is introduced via the atomization channel at a flow rate of 100 kg / h to 400 kg / h.

[0031] Preferably, the atomization gas is introduced via the atomization channel at a pressure of 0.1 bar to 2 bar

[0032] The melt is preferably obtained by continuously mixing a urea-containing melt and a melt containing elemental sulfur. Mixing additives that, for example, reduce the interfacial tension, viscosity, and / or density differences between the urea melt and the sulfur melt are unnecessary in the process according to the invention.

[0033] In a preferred embodiment, the granules contain 2% to 30% sulfur by weight, preferably 5% to 20% sulfur by weight. However, the final sulfur content can also be varied beyond the above-described range within the specifications for the final fertilizer granules.

[0034] In an alternative, preferred embodiment, the melt contains an additive that is amphiphilic relative to urea and elemental sulfur. The term "amphiphilic" describes an additive that has chemical / physical structural characteristics that enable good solubility in both the urea melt and the sulfur melt. Furthermore, the term "amphiphilic" is used analogously to its use in detergents and surfactants for oil / water mixtures. In addition to solubility, the additive enables, for example, the reduction of the interfacial tension as well as the viscosity and / or density differences between the urea melt and the sulfur melt.

[0035] The amphiphilic additive preferably comprises anionic, cationic or non-ionic surfactants, preferably salts and esters of fatty acids, SDS (sodium dodecyl sulfate), AOT (dioctyl sodium sulfosuccinate), lignin and / or ligninsulfonates and / or mixtures or derivatives thereof.

[0036] The melt preferably contains a granulation aid, particularly preferably formaldehyde or a formaldehyde-free granulation additive. The granulation aid reduces blockage, increases strength, and reduces the tendency of the granules to stick ("caking").

[0037] The formaldehyde-free granulation additive preferably contains a combination of at least one amino-containing polymer or oligomer and at least one functionalized polyvinyl compound, particularly preferably a combination of polyethyleneimine and polyvinyl alcohol. Amino-containing polymers and oligomers used according to the invention include, in particular, polymers and oligomers with a molecular weight (MW) of 250 to 2,000,000 Daltons. Examples of suitable amino-containing polymers and oligomers include polyamines, polymeric polyamines, nitrogen-substituted vinyl polymers, polyoxazolines, polypropyleneimine and its dendrimers, polyethyleneimine and its dendrimers, polyamidoamine and its dendrimers, as well as copolymers and derivatives and combinations of two or more of the substances mentioned.

[0038] Preferred amino group-containing polymers and oligomers include polyamines and polymeric polyamines, polyalkyleneimines such as polyethyleneimines and polypropyleneimines, polyvinylamines, polyalkoxylated polyamines, ethoxylated polyamines, propoxylated polyamines, alkylated and benzylated polyamines and combinations of two or more of the above-mentioned components.

[0039] Particularly preferred polymers and oligomers containing amino groups are polyethyleneimines, polyethyleneimine dendrimers, as well as their copolymers, derivatives and mixtures of at least two of these components.

[0040] Suitable polyethyleneimines may include linear or branched polyethyleneimine polymers or oligomers having, for example, 10 or more monomer units, as well as their derivatives, analogues, copolymers and mixtures of at least two of these components.

[0041] Polyethylenimines can be obtained by the polymerization of ethyleneimine and are commercially available on the market, for example in the form of the Lupasol ®< and Epomin ®< product families and in particular the products Lupasol ®< G20, Lupasol ®< FG, Lupasol ®< G35, Lupasol ®< P, and Lupasol ®< 1595 (the Lupasol ®< products are available from BASF (Florham Park, NJ, USA)), as well as Epomin ®< SP-003, Epomin ®< SP-006, Epomin ®< SP-012, Epomin ®< SP-018, Epomin ®< SP-200, Epomin ®< SP-1000, and Epomin ®< SP-1050 (the Epomin ®< products are available from Nippon Shokubai (Osaka, Japan)).

[0042] According to the invention, suitable functionalized polyvinyl compounds are, in particular, compounds based on the repeating unit (CH X CH Y ) n , in which X is selected from the group consisting of H, NH 2 , OH, COOH, COR, CONH 2 , CH 2 NH 2 , CH 2 NHR, CH 2 OH and CH 2 OR and Y is selected from the group consisting of NH 2 , OH, COOH, COR, CONH 2 , CH 2 NH 2 , CH 2 NHR, CH 2 OH and CH 2 OR and in which R each independently of one another represents alkyl, in particular C 1-6 alkyl, or aryl, in particular phenyl or pyridyl, which may be unsubstituted or optionally substituted with 1, 2, 3, 4 or 5 substituents independently of one another selected from the group consisting of F, Cl, Br, CF 3 , C 1-6 alkyl, C 1-6 alkoxy, NH 2 , C 1-6 alkyl, Amino and di(C1-6-alkyl)amino.

[0043] The functionalized polyvinyl compound used is preferably polyvinyl alcohol or polyvinylamine, or a mixture thereof. The functionalized polyvinyl compound is particularly preferably a polyvinylamine.

[0044] The polyvinylamine and the polyvinyl alcohol may each preferably have a molecular weight (MW) of 500 to 1,000,000 Daltons.

[0045] Suitable polyvinylamines include, in particular, linear polymers and copolymers derived from vinylformamide monomers and may include cationic and anionic polyvinylamine copolymers as well as charged and protonated polyvinylamines.

[0046] Suitable polyvinylamines are commercially available, for example those of the Lupamin ®< product family and in particular the products Lupamin ®< 1595, Lupamin ®< 4500, Lupamin ®< 5095, Lupamin ®< 9030, Lupamin ®< 9050 and Lupamin ®< 9095. Examples of cationic and anionic polyvinylamine copolymers are those of the Luredur ®< product family and in particular the products Luredur ®< Am na, Luredur ®< AV, Luredur ®< VH, Luredur ®< VI, Luredur ®< VM, Luredur ®< PR8094, Luredur ®< PR8261, and Luredur ®< PR8349. Examples of charged or protonated polyvinylamines are products of the Catiofast ®< product range, particularly Catiofast ®< GM, Catiofast ®< PL, Catiofast ®< PR8236, Catiofast ®< VCB, Catiofast ®< VFH, Catiofast ®< VLW, Catiofast ®< VMP, and Catiofast ®< VSH. The Lupamin ®< , Luredur ®< , and Catiofast ®< products are available from BASF (Florham Park, NJ, USA).

[0047] The formaldehyde-free granulating additive preferably contains at least: a combination of at least one amino group-containing polymer or oligomer and at least one functionalized polyvinyl compound, preferably a combination of polyethyleneimine and polyvinyl alcohol and / or a compound selected from the group of aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, aromatic dicarboxylic acids and anhydrides, preferably a compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride and / or an aliphatic C2-C8 dialdehyde, preferably ethanedial and / or glutaraldehyde.

[0048] The amphiphilic additive preferably contains a compound selected from the group of aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, aromatic dicarboxylic acids and anhydrides, preferably a compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride and / or at least one aliphatic C2-C8 dialdehyde, preferably ethanedial and / or glutaraldehyde.

[0049] In a preferred embodiment, the melt contains no added amphiphilic additive, as described above, in relation to urea and elemental sulfur. The absence of a blend additive reduces the cost of the finished fertilizer granules and avoids negative effects on the effectiveness of the fertilizer granules when taken up by plants.

[0050] Furthermore, the invention comprises the use of the fluidized bed granulator according to the invention described above for producing a fertilizer granulate comprising urea sulfur, urea, ammonium sulfate, UAS (urea ammonium sulfate), UAN (urea ammonium nitrate) and / or mixtures thereof.

[0051] The invention is further explained in more detail with reference to the following figures. These figures do not limit the scope of the invention, but serve only as examples. The figures are not to scale.

[0052] They show: Figure 1 a schematic cross-section through the spray nozzle according to the invention, Figure 2 a schematic plan view of the spray nozzle according to the invention and Figure 3 a further schematic cross-section of the spray nozzle according to the invention arranged in the perforated plate.

[0053] Figure 1shows a schematic cross-section through the spray nozzle (4) according to the invention, comprising a conveying channel (5) and an atomization gas channel (6). The spray nozzle (4) is characterized in that the conveying channel (5) has at least one separating pin (7). The atomization channel (6) has at least one swirling element (8). The melt (1) is divided in the region of the separating pin (7) and preferably turbulently swirled. This swirling surprisingly increases the homogeneity of the melt (1). The atomization gas (9) is passed through the spray nozzle (1) via the atomization channel (6).

[0054] The swirling elements (8) mounted in the atomization channel (6) increase the turbulence of the atomization gas (9), for example, air, passing through. If oxygen-sensitive granules are to be produced, gases / gas mixtures of noble gases, particularly argon, nitrogen, or carbon dioxide, can be used instead of air. The mixing of the melt (1) and the atomization gas takes place outside the outlet surface (3) of the spray nozzle (4). This mixing of the melt outside the spray nozzle (4) ensures particularly uniform particle growth.

[0055] Figure 2 shows a schematic top view of the spray nozzle (4) according to the invention, limited to the atomization channel (6) and delivery channel (5). The separating pins (7) are arranged crosswise.

[0056] Figure 3shows a further schematic cross-section of the spray nozzle (4) according to the invention arranged in the perforated plate (10). The spray nozzle comprises a conveying channel (5) and an atomization gas channel (6). The conveying channel (5) contains two intersecting separating pins (7), and the atomization channel (6) contains swirling elements (8). The melt (1) and the atomization gas (9) mix outside the flat outlet opening (3) and there, as microdroplets (11), strike the granulate particles (12) present in the fluidized bed (not shown). The granulate particles (12) grow to their final size (not shown) due to the deposition of the microdroplets (12) and are then removed from the fluidized bed granulator interior (2) (not shown). List of reference symbols

[0057] (1)Melt (2)Fluidized bed granulator interior (3)Exit surface (4)Spray nozzle (5)Conveying channel (6)Atomization channel (7)Separating pin (8)Swirling element (9)Atomization gas (10)Perforated plate (11)Melt droplets (12)Granule particles

Claims

1. Spray nozzle (4) for production of a urea fertilizer granules and / or urea-sulfur fertilizer granules at least comprising a conveying channel (5) and an atomizing gas channel (6), characterized in that the conveying channel (5) has at least one separating pin (7) which is designed as a single land or individually or multiply crossing lands, and the atomizing gas channel (6) has at least one swirl element (8) comprising fixed elements which are mounted in the atomizing gas channel (6), wherein the conveying channel (5) and the atomizing gas channel (6) are planar to one another and form a common exit opening (3) and wherein the atomizing gas channel (6) surrounds the conveying channel (5).

2. Fluidized bed granulator (2) comprising at least one spray nozzle (4) according to claim 1 disposed atop a perforated plate (10).

3. Process for the production of a urea-sulfur fertilizer comprising at least the steps of - providing a melt (1) containing urea and elemental sulfur; and - spraying the melt (1) and atomizing gas (9) into a fluidized bed granulator (3) with / via a spray nozzle (4); and - obtaining granules (14) in the fluidized bed granulator (3); characterized in that the spray nozzle (4) at least comprises a conveying channel (5) and an atomizing gas channel (6) having the features according to claim 1.

4. Process according to claim 3, characterized in that the spray nozzle (4) is maintained at a temperature in the temperature range from 1 °C to 10°C, preferably 2°C to 5 °C, above the crystallization temperature of the melt (2).

5. Process according to claim 3 or 4, characterized in that the melt (2) is introduced via the conveying channel (5) at a pressure of 0.5 bar to 7 bar and / or is introduced at a flow rate of 50 kg / h to 600 kg / h.

6. Process according to at least one of claims 3 to 5, characterized in that atomizing gas is introduced via the atomizing channel (6) at a flow rate of 50 kg / h to 400 kg / h and / or is introduced at a pressure of 0.1 bar to 2 bar.

7. Process according to at least one of claims 3 to 6, characterized in that the melt (1) is obtained by continuously mixing a urea-containing melt and an elemental sulfur-containing melt.

8. Process according to at least one of claims 3 to 7, characterized in that the granules (14) contain 2 wt.-% to 30 wt.-% sulfur, preferably 5 wt.-% to 20 wt.-% sulfur.

9. Process according to at least one of claims 3 to 8, characterized in that the melt (1) contains an additive which is amphiphilic with respect to urea and elemental sulfur.

10. Process according to claim 9, characterized in that the amphiphilic additive comprises anionic, cationic or nonionic surfactants, preferably salts and esters of fatty acids, SDS, AOT, lignin and / or lignosulfonates and / or mixtures and / or derivatives thereof.

11. Process according to one of claims 3 to 10, characterized in that the melt (1) does not contain an added additive which is amphiphilic with respect to urea and elemental sulfur.

12. Process according to one of claims 3 to 11, characterized in that the melt (1) contains a granulating auxiliary, preferably formaldehyde or a formaldehyde-free granulating additive.

13. Process according to claim 12, characterized in that the formaldehyde-free granulating additive contains a combination of at least one polymer or oligomer containing amino groups and at least one functionalized polyvinyl compound, preferably a combination of polyethyleneimine and polyvinyl alcohol.

14. Process according to claim 12 or 13, characterized in that the formaldehyde-free granulating additive contains at least - a combination of at least one polymer or oligomer containing amino groups and at least one functionalized polyvinyl compound, preferably a combination of polyethyleneimine and polyvinyl alcohol; and / or - a compound selected from the group of the aliphatic dicarboxylic acids and anhydrides, the aliphatic tricarboxylic acids and anhydrides, the aromatic dicarboxylic acids and anhydrides, preferably a compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride; and / or - an aliphatic C2-C8 dialdehyde, preferably ethanedial and / or glutaraldehyde.

15. Use of the fluidized bed granulator according to claim 2 for the production of a fertilizer granulate comprising urea-sulfur, urea, ammonium sulfate, UAS (urea-ammonium sulfate), UAN (urea-ammonium nitrate) and / or mixtures thereof.