FERTILIZER GRANULATE CONTAINING MAGNESIUM, SULPHATE AND UREA

Abstract

Disclosed is a spherical fertiliser granulate, which contains magnesium, sulphate and urea, each with respect to the total weight of the granulate, in the following quantities: Urea, calculated as elemental nitrogen, in a quantity of 20.0 to 38.0 wt %, magnesium, calculated as elemental magnesium, in a quantity of 1.5 to 9.5 wt % and sulphate, calculated as elemental sulphur, in a quantity of 2.7 to 12.0 wt %, wherein at least a portion of the magnesium, the urea and the sulphate is present in the form of at least one of the crystalline phases of the formulae MgSO.sub.4*6 NH.sub.2—C(═O)—NH.sub.2*0.5 H.sub.2O (I) and MgSO.sub.4*4 NH.sub.2—C(═O)—NH.sub.2*H.sub.2O (II), wherein 1 to 20 wt %, in particular 3 to 18 wt % and especially 5 to 15 wt % of the magnesium contained in the fertilizer granulate, calculated in each case as elemental magnesium, is present in the form of water-insoluble magnesium salts. Disclosed also is a process for manufacturing the fertiliser granulate as well as the use of the fertiliser granulate as fertiliser or in fertiliser mixtures.

Claims

1. Fertilizer granulate, which contains magnesium, sulphate and urea, each with respect to the total weight of the granulate, in the following quantities: urea, in a quantity of 20.0 to 38.0 wt %, calculated as elemental nitrogen; magnesium in a quantity of 1.5 to 9.5 wt %, calculated as elemental magnesium; and sulphate in a quantity of 2.7 to 12.0 wt %, calculated as elemental sulphur; wherein at least a portion of the magnesium, the urea and the sulphate is present in the form of at least one of the crystalline phases of the formulae (I) and (II)
MgSO.sub.4*6 NH.sub.2—C(═O)—NH.sub.2.0.5 H.sub.2O   (I)
MgSO.sub.4*4 NH.sub.2—C(═O)—NH.sub.2.H.sub.2O   (II) and wherein 1 to 20 wt % of the magnesium, with respect to the total quantity of the magnesium contained in the fertilizer granulate, calculated in each case as elemental magnesium, is present in the form of water-insoluble magnesium salts.

2. The fertilizer granulate according to claim 1, containing sulphate and urea in a ratio such that the mass ratio of nitrogen to sulphur is in the range of 1.8:1 to 10.5:1.

3. The fertilizer granulate according to claim 1, wherein a portion of the magnesium in the fertilizer granulate is present in the form of magnesium sulphate monohydrate, or in the form of magnesium sulphate 5/4-hydrate or as a mixture of magnesium sulphate monohydrate with magnesium sulphate 5/4-hydrate.

4. The fertilizer granulate according to claim 1, wherein 3 to 18 wt % of the magnesium, with respect to the total quantity of the magnesium contained in the fertilizer granulate, calculated in each case as elemental magnesium, is present in the form of water-insoluble magnesium salts.

5. The fertilizer granulate according to claim 1, wherein at least 10 wt % of the urea contained in the fertilizer granulate is present in the form of at least one of the crystalline phases of formulae (I) or (II).

6. The fertilizer granulate according to claim 1, wherein at least 70 wt % of the granule particles of the fertilizer granulate have a particle size in the range of 2 to 10 mm.

7. The fertilizer granulate according to claim 1, wherein the total amount of magnesium, sulphate and urea is at least 80 wt %, based on the total mass of the fertilizer granulate minus any water contained therein.

8. The fertilizer granulate according to claim 1, additionally containing a trace element from the group of boron, manganese, zinc, copper, iodine, selenium, cobalt, iron and molybdenum, preferably in a total amount of 0.1 to 5.0 wt %, with respect to the total mass of the fertilizer granulate.

9. The fertilizer granulate according to claim 1, wherein at least a portion of the urea in the granulate particles is present in the form of urea particles embedded in a matrix of sulphate salts of magnesium.

10. The fertilizer granulate according to claim 1, which does not contain more than 2% by weight of unbound water.

11. A process for producing a fertilizer granulate according to claim 1, which comprises providing a salt mixture containing a magnesium sulphate hydrate, a water insoluble magnesium salt and particulate urea, wherein the weight ratio of the total weight of magnesium salts to urea is in the range of 1.2:1 to 1:5 and wherein 1 to 20 wt % of the magnesium, with respect to the total quantity of the magnesium contained in the salt mixture and calculated in each case as elemental magnesium, is present in the form of water-insoluble magnesium salts, and subjecting the salt mixture to a granulation process in the presence of added water.

12. The process according to claim 11, wherein the magnesium sulphate hydrate and the water insoluble magnesium salt are provided as a solid reaction mixture obtainable by reaction of a caustic magnesium oxide or magnesium carbonate with a sub-stoichiometric amount of sulfuric acid.

13. The process according to claim 12, wherein the reaction mixture contains the water-insoluble magnesium salts in an amount from 0.5 to 7 wt %, based on the total weight of the solid reaction mixture and calculated as MgO.

14. The process according to claim 11, wherein the salt mixture contains water-insoluble magnesium salts in an amount from 3 to 18 wt %, based on the total quantity of the magnesium contained in the salt mixture and calculated in each case as elemental magnesium.

15. The process according to claim 11, wherein the salt mixture consists of at least 80 wt %, with respect to the total mass of the salt mixture minus any water contained therein, of magnesium sulphate hydrate, the water insoluble magnesium salt and urea.

16. The process according to claim 11, wherein the main quantity of water is added to the salt mixture before or at the beginning of the granulation process.

17. The process according to claim 11, wherein the amount of added water is 1.5 to 8 wt %, with respect to the mass of urea used for granulation.

18. The process according to claim 11, wherein at least 80% of the particular urea has a particle size in the range from 1 to 1000 μm.

19. The process according to claim 11, which is carried out as a press granulation of the salt mixture by means of a roller press in the presence of added water.

20. The process of claim 19, where the press granulation comprises providing the salt mixture containing a magnesium sulphate hydrate, a water insoluble magnesium salt and particulate urea by mixing, subjecting the obtained salt mixture to a compaction granulation to obtain granules and subsequently heating the granules.

21. The process of claim 20, wherein the granules are heated to a temperature in the range from 50 to 80° C.

22. The process according to claim 11, which is carried out as a mixed agglomeration process using an intensive mixer, in particular an Eirich mixer.

23. The process according to claim 22, wherein the agglomeration is performed at a temperature in the range of 55 to 80° C.

24. The process according to claim 22, wherein the agglomeration process is performed such that in the course of agglomeration the reaction mixture temporarily takes on a viscid form.

25. The process according to claim 22, wherein at least a portion of the water contained in the reaction mixture is removed during agglomeration.

26. A method for fertilizing soil, comprising applying a fertilizer granulate according to claim 1 as fertilizer or in fertilizer compositions to the soil being fertilized.

27. The method according to claim 26, wherein the NH.sub.3 emission of the fertilizer granulate is reduced.

Description

[0100] The following figures and examples serve to illustrate the invention:

[0101] FIG. 1: SEM image of a section of a representative granule from Example 2.

[0102] FIG. 2: SEM image of a representative granule from Example 4.

[0103] FIG. 3: SEM image of a representative granule from Example 5.

[0104] FIG. 4: X-ray powder diffractogram of a crushed granule from Example 2.

[0105] FIG. 5: X-ray powder diffractogram of a crushed granule from Example 4.

[0106] FIG. 6: X-ray powder diffractogram of a crushed granule from Comp. Example 5.

[0107] FIG. 7: X-ray powder diffractogram of a crushed granule from Example 24.

[0108] FIG. 8: SEM image of a representative granule from Example 24.

[0109] The burst strength or breaking strength was determined with the aid of the tablet breaking strength tester model TBH 425D from the ERWEKA company on the basis of measurements on 56 individual granules of different particle size (fraction 2.5-3.15 mm), and the mean value was calculated. The force required to break the granule between the punch and plate of the breaking strength tester was determined. Granules with a burst strength >400 N and those with a burst strength <4 N were not included in averaging.

[0110] Abrasion values were determined by a rolling drum process/method according to Busch. For this purpose, 50 g of the granulate with a particle size fraction of 2.5-3.15 mm were placed together with 70 steel spheres (diameter 10 mm, 283 g) in a tumble drum of a commercially available abrasion tester, e.g. ERWEKA, model TAR 20, and rotated for 10 min at 40 rpm (revolutions per minute). Subsequently, the contents of the drum were sieved using a sieve with a mesh size of 5 mm, under which a sieve with a mesh size of 0.5 mm was positioned, for 1 min on a sieving machine (model Retsch AS 200 control). The sieved fine fraction corresponds to the abrasion.

[0111] X-ray powder diffractometry: The respective granulate was crushed with a mortar and a pestle into a powder. The ground granulate was subsequently examined by X-ray powder diffractometry. The X-ray powder diffractogram was recorded with a Bragg-Brentano process diffractometer, model D 8, from the Endeavor company, AXS (298 K, Cu-K.sub.α-radiation: λ=1.5413 Å), increment: 0,018385738, increment duration: 0.2 seconds, detector: Lynx Eye, reflection geometry in range 2θ=8°-70°. The specified lattice distances were calculated from the determined 2θ values.

[0112] The composition of the granulate was determined by the following methods: [0113] N-determination: association method VDLUFA II.1—Association of German Agricultural Analytic and Research Institutes e.V. (VDLUFA), 3.5.2.7 and association method VDLUFA 11,1, 3.9.2*, [0114] Mg/S determination: association method VDLUFA (K+S 0905.01), [0115] Boron/zinc determination: DIN EN ISO 11885 (E22), [0116] H.sub.2O determination by Karl Fischer titration.

[0117] The amount of water-insoluble magnesium sulfate was determined indirectly by first determining the total magnesium content, by completely dissolving the crushed material in deionized water containing 1 wt % of nitric acid and the determining the amount of magnesium in the aqueous solution as above. Then, a second portion of the crushed material is dissolved in deionized water of pH 7 at 22° C. for 24 h with stirring. The insoluble matter is removed by filtration and the amount of magnesium in the aqueous solution is determined by elemental analysis. The difference between the total amount of magnesium and the amount of soluble magnesium is the amount of insoluble magnesium.

[0118] The granulate was embedded in epoxy resin for sample preparation for the SEM or EDX examination. After curing of the two-component resin, the samples were ground planar using silicon carbide. The samples were not vaporised with electrically conductive layers.

[0119] The SEM images were taken with an EVO 50EP scanning electron microscope from the company CARL ZEISS SMT (SE detector, VPSE G3 detector, LM4Q BSD).

[0120] The EDX was performed with the “Noran System Six” microanalyser system with an LN.sub.2-cooled detector with a resolution of 129 eV for MnK.sub.α from the company Thermo. The system is integrated in the SEM.

[0121] For the preparation of the fertilizer granulate of examples 1 to 4 and 6 to 9, a synthetic magnesium sulphate monohydrate (SMS-1) was used, which was prepared in the following manner:

[0122] Calcined magnesite (MgO-content about 80-85%) was reacted with about 70 wt % aqueous sulphuric acid in a molar ratio Mg:H.sub.2SO.sub.4 of about 0.9. The product thereby obtained, with a temperature of about 115-120° C., was taken directly behind the mill of the reactor. The magnesium sulphate granulate thereby obtained had a total magnesium-content of at least 27 wt %, calculated as MgO, and a content of water-soluble magnesium of at least 25 wt %, calculated as MgO. The amount of water-insoluble magnesium salts was 2 wt %. The SMS thereby obtained contained less than 10 wt % of particles having a particle size <2 microns and less than 10 wt % of particles having a particle size of >250 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0123] For the preparation of the fertilizer granulate of comparative example 5, a mixture of two kieserite fractions was used in the mass ratio 1:1, comprising a fine (kieserite M) and a coarser (kieserite E) with the following particle size distributions: kieserite M contained less than 10 wt % of particles with a particle size <5 microns and less than 10 wt % of particles having a particle size of >250 microns (determined by laser light diffraction according to ISO 13320:2009-10). Kieserite E contained less than 10 wt % of particles with a particle size <100 microns and less than 10 wt % of particles having a particle size of >900 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0124] For the preparation of the fertilizer granulate of examples 12, 16, 20, 24, 25, 27, 28, 29, 32 and 33, a synthetic magnesium sulphate monohydrate (SMS-2) was used, which was prepared from calcined magnesite by analogy to SMS-1. It contained less than 10 wt % of particles having a particle size <100 microns and less than 10 wt % of particles having a particle size of >300 microns (determined by laser light diffraction according to ISO 13320:2009-10). The SMS-2 contained 2 wt % of water insoluble magnesium, calculated as MgO, and had a total magnesium content of 27 wt %, calculated as MgO.

[0125] For the preparation of the fertilizer granulate of example 36 and 37, a synthetic magnesium sulphate monohydrate (SMS-3) was used, which was prepared from calcined magnesite by analogy to SMS-1. It contained 90 wt % of particles having a particle size of mesh 40-60 (250-420 μm, determined by laser light diffraction according to ISO 13320:2009-10). The SMS contained 2.7 wt % of water insoluble magnesium, calculated as MgO, and had a total magnesium content of 27%, calculated as MgO.

[0126] In comparative examples 9, 13, 17, 21, 26, 30, 31, 34 and 35, a kieserite was used, which contained less than 10 wt % of particles with a particle size <70 microns and less than 10 wt % of particles having a particle size of >300 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0127] In comparative examples 11, 14, 18 and 22, a magnesium sulphate dihydrate was used, which contained less than 10 wt % of particles with a particle size <70 microns and less than 10 wt % of particles having a particle size of >300 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0128] In comparative examples 10, 15, 19 and 23, a magnesium sulphate trihydrate was used, which contained less than 10 wt % of particles with a particle size <70 microns and less than 10 wt % of particles having a particle size of >300 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0129] For urea, a commercially-available prilled urea was used with a nitrogen-content of 46 wt %. The prill was ground to a powder containing less than 10 wt % of particles having a particle size <5 microns and less than 10 wt % of particles having a particle size of >300 microns (determined by laser light diffraction according to ISO 13320:2009-10).

[0130] In Examples 6 and 8, a finely divided zinc sulphate monohydrate having a content of 35.0 wt % of zinc and a sulphur content of 17.0 wt % was used.

[0131] In Example 8, a commercially-available borax pentahydrate was used with a boron content of 14.0 wt %.

[0132] In Example 7, the boron source used was a calcined ulexite (CaNa[B.sub.5O.sub.6(OH).sub.6].5 H.sub.2O) with a boron content of 14.9 wt %.

[0133] The granulation described below in examples 1 to 8 (group A of embodiments) was performed in an intensive mixer from the company Maschinenfabrik Gustav Eirich GmbH & Co. KG (model intensive mixer R01), hereinafter known as “Eirich mixer”. The Eirich mixer had a filling volume of 5 L. Per preparation about 2 to 2.5 kg of salt mixture were used.

EXAMPLE 1

[0134] 52.3 parts by weight of SMS-1 were placed in an intensive mixer from the Eirich company and heated to 75° C. This was followed by addition of 45.2 parts by weight of urea and mixing at a speed of 600 rpm for 5 minutes, initially adding 2.5 parts by weight of water in countercurrent. In this case, the mixture became increasingly liquid and had a viscid consistency. Subsequently, the stirring speed was reduced to 100-200 rpm to promote granulate formation. From this point on, the mixture was allowed to cool for a period of 10 min., and the excess water produced by the reaction was removed via a turbulent air stream. At temperatures below 60° C., the mass hardened to form a solid granulate.

[0135] Examples 2 to 8 were performed in an analogous manner but with a modified salt composition. The salt composition used in each case and the amount of added water are summarised in Table 4. The compositions of the granulate determined according to elemental analyses are listed in Table 5. The mechanical properties of the granulate obtainable according to the invention are summarised in Table 6.

[0136] In all examples, the crystalline phase of formula (I) could be detected by X-ray powder diffractometry (see also FIGS. 4 to 6).

TABLE-US-00004 TABLE 4 feedstock materials/input materials Magnesium sulphate Urea Water Micronutrients Example [PBW].sup.1) [PBW] [PBW] [PBVV] 1 SMS-1 52.3 45.2 2.5 — — 2 SMS-1 42.2 54.8 3.0 — — 3 SMS-1 35.4 61.2 3.4 — — 4 SMS-1 17.3 78.5 4.2 — — 5 .sup.2) Kieserite 40.5 57.0 2.5 — — 6 SMS-1 37.0 54.3 3.0 ZnSO.sub.4 .Math. H.sub.2O 5.7 7 SMS-1 37.7 49.0 3.0 calc. ulexite 10.3 8 SMS-1 38.8 53.5 1.5 ZnSO.sub.4 .Math. H.sub.2O + Na2BO7 .Math. 5 H.sub.2O 2.9 + 3.3 .sup.1)BW = parts by weight .sup.2) Comparative Example

TABLE-US-00005 TABLE 5 Elemental composition of the granulate: Mg tot .sup.1) Mg ws .sup.2) S N B Zn Example [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] 1 8.51 7.88 10.40 20.79 0 0 2 6.88 6.37 8.40 25.20 0 0 3 5.76 5.34 7.04 28.16 0 0 4 2.81 2.61 3.44 36.12 0 0 5 .sup.3) 6.60 6.60 8.73 26.19 0 0 6 6.02 5.58 8.33 24.98 0 2.00 7 6.15 5.69 7.51 22.52 1.53 0 8 6.20 5.74 7.58 22.73 0.50 1.00 .sup.1) Mg tot: Magnesium, total .sup.2) Mg ws: Magnesium, water soluble .sup.3) Comparative Example

TABLE-US-00006 TABLE 6 Mechanical properties of the granulate: Burst strength Abrasion Example [N] [%] 1 45 0.1 2 40 0.1 3 39 0.1 4 34 0.3 5* 20 0.2 6 42 0.1 7 51 0.4 8 47 0.4 *Comparative Example

[0137] A SEM examination of a granulate from Example 2 gave the following result—see FIG. 1. The grain had a regular shape and was a conglomerate of several particulate components embedded in a matrix of another material. A cross section is shown in FIG. 1. The particulate components of the grain and the matrix were analysed for elemental composition by EDX. The components appearing evenly dark in the figure (arrow 1) were identified as urea due to the associated elemental composition. The particulate components (arrow 3) appearing white coloured were identified as magnesium sulphate monohydrate. The matrix consisted largely of the crystalline phase of formula (I) (arrow 2).

[0138] SEM studies of representative grains of Example 4 (FIG. 2) and Example (5) (FIG. 3) gave a result comparable to Example 2. In FIGS. 2 and 3, arrow 1 points to a region which, according to EDX analysis, consists essentially of urea. Arrow 2 indicates a region which, according to EDX analysis, consists essentially of the crystalline phase of formula (I) and arrow 3 indicates an area consisting essentially of magnesium sulphate monohydrate.

[0139] FIG. 4 shows an X-ray powder diffractogram taken from crushed granulate of Example 2. The presence of the crystalline phase of formula (I), urea and magnesium sulphate monohydrate (kieserite) was detected on the basis of the reflections characteristic of the respective phase.

[0140] FIG. 5 shows an X-ray powder diffractogram taken from crushed granulate of Example 4. The presence of the crystalline phase of formula (I), urea and magnesium sulphate monohydrate (kieserite) was detected on the basis of the reflections characteristic of the respective phase.

[0141] FIG. 6 shows an X-ray powder diffractogram taken from crushed granulate of Comparative Example 5. The presence of the crystalline phase of formula (I), urea and magnesium sulphate monohydrate (kieserite) was detected on the basis of the reflections characteristic of the respective phase.

[0142] In FIGS. 4 to 6, the reflections characteristic of the respective crystalline phase are indicated as follows: [0143] .box-tangle-solidup. Crystalline phase of formula (I) [0144] .square-solid. Urea [0145] .circle-solid. Magnesium sulphate monohydrate (kieserite)

[0146] FIG. 7 shows an X-ray powder diffractogram taken from crushed granulate of Example 24. The presence of the crystalline phase of formula (II), urea and magnesium sulphate monohydrate (kieserite) was detected on the basis of the reflections characteristic of the respective phase.

[0147] In FIG. 7, the reflections characteristic of the respective crystalline phase are indicated as follows: [0148] .diamond-solid. Crystalline phase of formula (II) [0149] .square-solid. Urea [0150] .Math. MgSO.sub.4.H.sub.2O (Kieserite phase)

[0151] Comparative Examples 9, 10, 11, 13, 14, 15, 17, 18, 19 and inventive examples 12, 16 and 20: Group A of embodiments

[0152] Examples 9 to 20 were carried out by analogy to the protocol of example 1 using a intensive mixer with a rotating mixer and a rotating barrel having an internal volume of 50 L and a hot air heating jacket. The rotating mixer was operated with a rotation speed of 800 rpm and the barrel with a rotating speed of 27 rpm. Urea and the respective magnesium sulphate hydrate were added to the barrel and heated to the temperature T1 given in Table 7. Heated water was added to the barrel at the beginning of the process. The mixture was mixed for mixing time t.sub.mix. At the end of the mixing excess water produced by the reaction was removed via a turbulent air stream. In examples 10-20 the granules were held for 6-12 h at the temperature T2.

[0153] The amounts of urea and added water, the type and amount of magnesium sulphate hydrate and the temperatures are given in the following Table 7:

TABLE-US-00007 TABLE 7 Urea MgSO.sub.4 Water T1 T2 t.sub.mix Ex. [kg] type .sup.1) [kg] [%] .sup.2) T [° C.] [° C.] [° C.] [min]  9.sup.3) 5.0 A 5.0 4.90 60 68 -- 16.0 10.sup.3) 5.0 B 5.0 4.00 65 71 60 23.0 11.sup.3) 5.0 C 5.0 1.68 70 68 62 10.5 12 5.0 D 5.0 4.60 57 74 68 14.5 13.sup.3) 7.4 A 3.7 4.55 64 71 71 24.0 14.sup.3) 7.4 C 3.7 1.80 61 72 70 16.5 15.sup.3) 7.4 B 3.7 3.20 62 70 59 15.0 16 8.0 D 4.0 4.83 60 76 78 26.5 17.sup.3) 8.25 A 5.5 4.00 58 72 67 17.5 18.sup.3) 8.25 C 5.5 1.09 60 72 61 10.0 19.sup.3) 8.25 B 5.5 2.18 62 80 62 11.0 20 9.75 D 6.5 2.95 63 65 63 24.5 .sup.1) A: kieserite; B: magnesium sulphate trihydrate; C: magnesium sulphate dihydrate; D: SMS-2 .sup.2) wt % of water with respect to the total amount of urea and magnesium sulphatehydrate .sup.3)comparative examples containing less than 0.1 wt % of water-insoluble magnesium salts with respect to the total amount of magnesium, calculated was Mg.

Comparative Examples 21 to 23 and Inventive Example 24:Group B1 of Embodiments

[0154] The granulate was prepared according to the following protocol: [0155] (1) In a heatable intensive mixer with a capacity as described for example 9 urea and magnesium sulphate were added at ambient temperature and intensively mixed for the mixing time given in table 8 with the desired amount of water having ambient temperature. [0156] (2) Subsequently, the mixture was evenly fed into a laboratory press and compacted. A double roller press was used for this purpose, which had two counter-rotating rollers (diameter 140 mm, length 200 mm) with trough-shaped recesses (length 6 mm×width 6 mm×depth 1.6 mm). The press was operated with a roller speed of 72 rpm. The specific press force was individually adjusted for each test, taking care to obtain a uniform scabbing flakes, which was crushed by means of crusher followed by sieving to remove fines of a diameter below 2 mm. The salt mixture was fed by means of a plug screw arranged above the press rolls. The feed rate of mixture was about 10 to 20 kg/min. [0157] (3) The mini briquettes obtained in step (2) were heated in a vented oven for 6-12 h to the temperature T3 given in Table 8. [0158] (4) The heated briquettes were cooled to ambient temperature and subjected to grain separation and rounding of the individual grains . [0159] (5) The material obtained in step (4) was then screened. The screening was carried out in the grain size range 4.5-5.6 mm, which represents the product fraction. The fraction with grain size <4.5 mm can be fed back to the feed in step (2) (fine material). The fraction with grain size >5.6 mm (coarse material) can be fed back into the step (4).

TABLE-US-00008 TABLE 8 Urea MgSO.sub.4 Water T3 t.sub.mix Ex. [kg] type .sup.1) [kg] [%] .sup.2) T [° C.] [° C.] Ex. 21.sup.3) 10.0 A 5.0 2.33 25 70 16.0 22.sup.3) 10.0 C 5.0 2.00 25 70 23.0 23.sup.3) 10.0 B 5.0 1.33 25 70 10.5 24 15.0 D 7.5 2.22 25 70 14.5 .sup.1) A: kieserite; B: magnesium sulphate trihydrate; C: magnesium sulphate dihydrate; D: SMS-2 .sup.2) wt % of water with respect to the total amount of urea and magnesium sulphate hydrate .sup.3)comparative examples

[0160] The granules obtained in examples/comparative examples 9 to 24 were analysed with X-ray powder diffractometry as described above. In each of the probes, the crystalline phase of the formula (II) was present. The intensity of the reflections indicated that the phase of the formula (II) was present in an amount of at least 10 wt % of the granulate. In addition, the characteristic reflections of crystalline urea were observed in each of the granules, indicating that non-reacted urea was present. In the granulate of examples 12, 16, 20 and 24 the kieserite phase was observed. In comparative Examples 9, 10, 11, 13, 14, 15, 17, 18, 19 the phase of formula (IV) was present in amounts of at least 10 wt % of the granulate, while it was absent or less pronounced in the granulates of inventive examples 12, 16 and 20.

[0161] A SEM examination of a granulate from Example 24 gave the following result—see FIG. 8. The grain was a conglomerate of several particulate components embedded in a matrix of another material. A cross section is shown in FIG. 8. The components of the grain and the matrix were analysed for elemental composition by EDX. The components appearing evenly dark in the figure (arrow 1) were identified as urea due to the associated elemental composition. The matrix consisted partly of the crystalline phase of formula (II) (arrow 2) and also of magnesium sulphate monohydrate (arrow 3). In addition, particles of Mg containing silicates (arrow 4) and MgO (arrow 5) were present.

Examples 25, 27 to 29, 32, 33, 34, 36 and 37 and Comparative Examples 26, 30, 31, 34 and 35: Group B1 of Embodiments

[0162] The granulate was prepared by analogy to the protocol of examples 21 to 24 using a large scale granulation equipment and a rotary heater and cooler for heating and cooling the granulate exiting the double roller press. The relative amounts of urea, magnesium sulphate hydrate and water, the mixing time and the heating temperature are summarized in Table 9.

TABLE-US-00009 TABLE 9 Urea/MgSO.sub.4 Water T3 t.sub.mix Ex. Type MgSO.sub.4 .sup.1) (w/w) [%] .sup.2) T [° C.] [° C.] [min] 25 D 1:1 2-3 25 60-70 5 26.sup.4) A 1:1 2-3 25 60-70 5 27 D 1:1 2 25 50 5 28 D 1:1 2 25 60 5 29 D 1:1 2 25 65 5 30.sup.3) A 1:1 3 25 60 5 31.sup.3) A 1:1 3 25 65 5 32 D 2:1 2-3 25 60-70 5 33 D 4:1 2-3 25 60-70 5 34.sup.3) A 2:1 2-3 25 60-70 5 35.sup.3) A 4:1 2-3 25 60-70 5 36 D# 1:1 2 25 60 5 37 D# 1:1 2 25 65 5 .sup.1) A: kieserite; D: SMS-2 D#: SMS-3 .sup.2) wt % of water with respect to the total amount of urea and magnesium sulphate hydrate .sup.3)comparative examples

[0163] The granules obtained in examples/comparative examples 27 to 37 were analysed with X-ray powder diffractometry as described above. In each of the examples, the crystal-line phase of the formula (I) was present, except for comparative example 34. In examples 27, 32, 33, 36 and 37 and in comparative example 34 a crystalline phase of the formula (II) was observed. The intensity of the reflections indicated that the phases of the formulae (I) and (II) were present in an amount of a least 5 wt % of the granulate. In addition, the characteristic reflections of crystalline urea were observed in each of the granules, indicating that each of theses phases were present in an amount of a least 10 wt % of the granulate. In comparative examples 31, 32, 34 and 35 the crystalline phases of formulae (III) and (IV) were clearly present, while they were absent or less pronounced in examples 27 to 29, 32, 33, 36 and 37. In the granulate of examples 27 to 29, 32 and 33 the kieserite phase was present.

TABLE-US-00010 TABLE 10 Elemental composition Mg tot .sup.1) Mg ws .sup.2) N S Moisture Example [wt %] [wt %] [wt %] [wt %] [wt %] 25 9.20 n.d. 20.20 n.d. .sup.3) 0.9 26.sup.4) 7.90 7.90 22.70 n.d.  0.5 29 9.35 8.39 n.d. 10.83  0.2 31.sup.4) 8.24 8.24 n.d. 11.20  0.1 32 6.34 5.32 n.d. 7.27 0.4 33 4.06 3.52 n.d. 4.33 0.2 34.sup.4) 5.21 5.19 n.d. 6.87 0.1 35.sup.4) 3.51 3.49 n.d. 4.80 0.1 .sup.1) Mg tot: Magnesium, total .sup.2) Mg ws: Magnesium, water soluble .sup.3) n.d.: not determined .sup.4)comparative examples

TABLE-US-00011 TABLE 11 Mechanical properties of the granulate: Burst strength Abrasion Example [N] [%]  9.sup.2) 29  n.d. .sup.1) 12 51 n.d. 13.sup.2) 25 n.d. 14.sup.2) 25 n.d. 16 41 n.d. 17.sup.2) 27 n.d. 20 43 n.d. 21.sup.2) 21 n.d. 22.sup.2) 16 n.d. 23.sup.2) 16 n.d. 24 24 n.d. 25 52 n.d. 26.sup.2) 22 n.d. 27 35 n.d. 28 32 1.4 29 31 n.d. 30.sup.2) 20 n.d. 31.sup.2) 21 n.d. 32 24 0.0 33 22 0.0 34.sup.2) 19 1.1 35.sup.2) 13 4.0 36 29 1.4 37 30 1.6 .sup.1) n.d.: not determined .sup.2)not according to the invention

Test Procedure for Determining the NH.SUB.3 .Emission of the Granulate

[0164] To determine the NH.sub.3 emission of the granulate, a sample of the respective fertilizer was applied to a defined amount of soil in a sealable, airtight vessel (soil with 63 soil points as representative average, moisture of the soil was about 16 wt %). The lid of the vessel was a pierced rubber stopper through which a Dräger tube for detection of ammonia protruded into the interior of the vessel. Depending on the degree of NH.sub.3 emission, a colour change from yellow to blue can be observed after some time with the Dräger tube due to the formation of ammonia as the decomposition product of the fertilizer. The height of the blue-coloured portion in the Dräger tube correlates with the amount of ammonia formed.

[0165] As a product according to the invention, the granulate from Example 2 was tested. As a reference, a sample of pure urea and a commercial urea-based fertilizer with urease inhibitor (UI) was used, each with the exact same total amount of urea as in the experiment with the granulate from Example 2. Comparison of all Dräger tubes showed that the largest total amount of ammonia formed when using pure urea as fertilizer. In the granulate from Example 2, an average ammonia formation was observed. The lowest amount of ammonia was found in the commercial fertilizer with UI admixture.