WATER SOLUBLE COMPLEX FERTILISERS, METHOD FOR THEIR PREPARATION AND RELATED USE

Abstract: The present invention relates to a method for the preparation of a complex NPK fertiliser in the form of granules or prills, and to a method for its preparation and to the related use of the fertiliser thereby obtained. In particular the present invention relates to a fertiliser containing as fertilising elements Nitrogen N, Phosphor P, Potassium K, meso elements like Calcium Ca, Magnesium Mg, Sulphur S, and micro elements like Iron Fe, Manganese Mn, Zinc Zn, Copper Cu, Boron B and Molybdenum Mo.

Description: Description Water Soluble Complex Fertilisers. Method for their Preparation and Related Use Technical Field The present invention relates to a complex NPK fertiliser in the form of granules or prills, and to a method for its preparation and to the related use of the fertiliser thereby obtained. In particular, the present invention relates to a fertiliser containing as fertilising elements Nitrogen N, Phosphor P, Potassium K, meso elements like Calcium Ca. Magnesium Mg, Sulphur S, and micro elements like Iron Fe, Manganese Mn, Zinc Zn, Copper Cu, Boron B and Molybdenum Mo. Background Art Complex NPK fertilisers containing meso and micro elements are known in the trade. These types of fertilisers are obtained by etching phosphatic rocks with sulphuric, nitric or phosphoric acid with the subsequent ammonification and addition of Potassium in the form of potassium sulphate or potassium chloride to obtain a suspension or pulp. The solution or pulp is then transformed into solid particles shaped as granules or prills, by means of granulating processes or through the prilling of the molten salts. Although these kinds of fertilisers contain in full or in part the nutrients necessary for crops, they are not free of disadvantages. One disadvantage is that of not being perfectly water soluble due to the presence of the residues deriving from the etching of the phosphatic rocks, i.e. if solubilised they leave an insoluble residue. The direct application of the solution of complex NPK fertilisers thereby obtained causes the blockage of distribution systems in fertilisation-irrigation, leaf fertilisation, and hydroponic fertilisation systems. There are patents that relate to the production of water soluble complex NPK fertilisers that contain meso and micro elements. All such methods provide for obtaining a solution of molten salts containing N, generally NH 4 NO ; „ with the subsequent addition of solid salts containing P such as NH 4 H : PO 4 or (NH 4 ) 2 HPO 4 and/or K such as K 2 S0 4 and KCl. The limitation for these methods consists of the fact that the added phosphatic and/or potassic salts are in solid fonn and can give rise to a suspension, leading to problems of inconsistency in the molten solution in addition to high viscosity levels, which as is well known prevent the perfect homogenisation of the solution. It is known that the production of highly soluble complex NPK fertilisers available on the market is carried out by mixing the various sources of N, P, K, perfectly soluble meso and micro elements, after grinding the components to obtain a uniform grain size. This common practice presents two disadvantages. The first disadvantage is that the product thereby obtained contains dusts due to the grinding, creating problems in any direct application. The second disadvantage is that of having to mix together components having different density with the consequent problems of component segregation during the preparation, transport, storage of the sacks and during the mechanical distribution on the soil. Also commercially available are products which do not present segregation or dustiness problems, both in the form of granules, prills or crystals which are perfectly water soluble, but bring to the crops only two nutrients among N, P, and K and at times meso and micro elements. I.e.. NP, KP. and NK fertilisers are available. It is also well known that all fertilisers have the tendency to become compacted due to the irregularity of the particles, lack of homogeneity of the particles, and residual humidity. Disclosure of Invention One of the aims of the present invention is to provide a method which allows to obtain a water soluble complex NPK fertiliser in granules or prills, highly soluble in water, which may contain meso and micro elements and has perfectly predictable composition characteristics since each granule or prill derives from a solution with homogeneous composition. Another aim of the proposed method is to provide a water soluble complex NPK fertiliser in granules or prills, which does not present segregation phenomena during the preparation, transport or storage of the sacks and in the course of mechanical distribution on the soil, and which contains no dust. Yet another aim of the proposed method is to provide a water soluble complex NPK fertiliser in granules or prills which can be used in localised fertilisation- irrigation or in widespread fertilisation-irrigation, leaf fertilisation, hydroponic fertilisation, or usable also when the immediate availability of nutrients is required, but no specific application device is available and the product is distributed on the soil, with subsequent irrigation by traditional methods. A further aim of the method proposed by the present invention is to provide a water soluble complex NPK fertiliser in granules or prills, having such composition and homogeneity characteristics as to provide it with greater resistance against compacting. Description of the Illustrative Embodiment These aims and others beside have been achieved by the Applicant which has found it useful to prepare a water soluble complex NPK fertiliser in the form of granules of prills by means of a method which comprises the following phases: a) solubilisation in water of salts containing the fertilising elements of Nitrogen, Phosphor, and Potassium to form a solution, said solution comprising a fraction of non soluble solids in suspension; b) separation from the solution obtained during phase a) of the fraction of non soluble solids in suspension, thus obtaining a solution free of solids in suspension; c) concentrating the solution free of solids in suspension obtained from phase b) until obtaining a solution; and d) cooling the solution obtained from phase c) until obtaining granules or prills. The method consists of the solubilisation in water, during phase a), of salts containing the fertilising elements N, for instance in the form of ammonium nitrate (NH 4 NO 3 ), Phosphor, for instance in the form of mono-ammonium phosphate (NH 4 H 2 PO 4 ) and Potassium, for instance in the form of potassium nitrate KNO 3 . From said solution is separated, during phase b), the fraction of the non soluble solids in suspension, thereby obtaining a solution without solids in suspension. Preferably said solution without solids in suspension contains no more than 80% of water weight. Possibly, to obtain the required composition, to the solution can be added other fertilising elements N. P, K and nutrients (meso and micro elements) such as S. Ca. Mg, Fe, Mn. Zn. Cu. B. Mo contained in water soluble salts. The solution is concentrated by means of heating, during phase c), until obtaining a solution of molten salts. Preferably said solution of molten salts has a maximum water content of 5% by weight. The molten salt solution thereby obtained is then cooled, during phase d), in such a way as to obtain granules or prills having a size smaller than 7 mm; preferably smaller than 4 mm. The method of the present invention allows to obtain a complex NPK fertiliser in the form of granules or prills having a solubility in water of at least 90% by weight; preferably at least 95% by weight; yet more preferably, at least 99% by weight. The complex NPK fertilisers of the present invention present the advantage of having pronounced anti-compacting characteristics. Moreover, the complex NPK fertilisers of the present invention are free of dusts. The complex NPK fertilisers of the present invention can be used in applications of localised fertilisation-irrigation or widespread fertilisation-irrigation, leaf fertilisation, hydroponic fertilisation, or can be used also when the immediate availability of nutrients is required but no specific application device is available and the product is distributed on the soil, with subsequent irrigation by traditional methods. Some preferred embodiments of the method according to the present invention are described below with reference to the flow chart shown in Figure 1. Said preferred embodiments are provided by way of non limiting examples and they are as follows: A) the raw materials containing non water soluble solids 1 are dissolved in water with all raw materials which are perfectly soluble in water 7 until the required ratios are obtained. Subsequently, the resulting solution 2 is separated in two fractions, obtaining the resulting clear solution 3 and the insoluble body 10. If integrations to the formulation are required, they are carried out when mixing between the flows 3 and 8; if no integration is required, the homogenisation (mixing) phase can be eliminated, directly obtaining flow 4 from flow 3. B) The raw materials containing non water soluble solids 1 are dissolved in water separately from the perfectly water soluble raw materials 5. The resulting solution 2 is separated in two fractions, obtaining the resulting clear solution 3 and the insoluble body 10. The flows 3 and 6 are mixed. If necessary, during this phase the formulation is integrated by means of the flow 8. The current 4 is thereby obtained at the output. C) The raw materials containing non water soluble solids 1 are dissolved in water together with some of the water soluble raw materials 7. Subsequently, the resulting solution is separated in two fractions, obtaining the clear solution 3 and the insoluble body 10. Some of the perfectly water soluble raw materials 5 are solubilised in water, obtaining the flow 6. The flows 3 and 6 are mixed together and the rest of the perfectly water soluble raw materials 8 are added thereto in order to integrate the solution with the required elements. The addition of the integrating elements 8 can be carried out directly also in the flow 3 or in the flow 6 in a separate manner, before the total mixing of the various flows, guaranteeing in all cases the perfect solubilisation of said elements in the solution. Alternatively one or more fully soluble salts containing nutrients (meso and/or micro elements) and/or one or more fully soluble salts containing the fertilising elements N, P, K, instead of being subjected to a prior solubilisation, are dissolved directly, partly during the solubilisation phase a) and partly solubilised in the solution obtained after the separation phase b). Alternatively one or more fully soluble salts containing nutrients (meso and/or micro elements) and/or one or more fully soluble salts containing the fertilising elements N. P, K, instead of being subjected to a previous solubilisation, are dissolved directly in the solution 3 obtained after separating the solids. Alternatively one or more fully soluble salts containing nutrients (meso and/or micro elements) and/or one or more fully soluble salts containing the fertilising elements N, P, K, are divided into three flows, a first flow is added to the solubilisation phase a), a second flow is added to the solubilisation phase a'), and a third flow is solubilised directly in the solution obtained from phase b).

Claims: Claims 1. A method for preparing water soluble fertilisers in the form of granules or prills comprising as fertilising elements Nitrogen, Phosphor and Potassium, characterised in that it comprises the following phases: a. solubilisation in water of salts containing the fertilising elements of Nitrogen, Phosphor, and Potassium to form a solution, said solution comprising a fraction of non soluble solids in suspension; b. separation from the solution obtained during the phase a) of the fraction of non soluble solids in suspension, thus obtaining a solution free of solids in suspension; c. concentrating the solution free of solids in suspension obtained from the phase b) until obtaining a solution; and d. cooling the solution obtained from the phase c) until obtaining granules or prills. 2. The method as claimed in claim 1 , characterised in that the salt of the Nitrogen fertilising element solubilised during the phase a) is ammonium nitrate. 3. The method as claimed in claim 1 , characterised in that the salt of the Phosphor fertilising element solubilised during the phase a) is mono-ammonium phosphate. 4. The method as claimed in claim 1, characterised in that the salt of the Potassium fertilising element solubilised during the phase a) is potassium nitrate. 5. The method as claimed in claim 1, characterised in that the solution free of salts in suspension obtained from the phase b) has a water content not exceeding 80% by weight. 6. The method as claimed in claim 1, characterised in that the solution in the phase c) is concentrated until having a water content not exceeding 5% by weight. 7. The method as claimed in claim 1 , characterised in that during the solubilisation phase a) also one or more soluble salts are dissolved, containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu, B and Mo. 8. The method as claimed in claim 1 , characterised in that during the solubilisation phase a) also one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen. Phosphor and Potassium are dissolved. 9. The method as claimed in claim 1. characterised in that it comprises a solubilisation phase a') separate from the phase a) during which one or more soluble salts containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu. B and Mo are dissolved and a mixing phase during which, before the concentration phase c), the solutions obtained respectively from the phase b) and from the phase a') are mixed together. 10. The method as claimed in claim 1 , characterised in that it comprises a solubilisation phase a') separate from the phase a) during which one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen, Phosphorus and Potassium are dissolved and a mixing phase during which, before the concentration phase c), the solutions obtained respectively from the phase b) and from the phase a') are mixed together. 1 1. The method as claimed in claim 1 , characterised in that the during the solubilisation phase a) a first portion of one or more soluble salts containing nutrients selected from the group consisting of S, Ca. Mg, Fe, Mn, Zn, Cu, B and Mo is dissolved, while a second portion of said soluble salts is dissolved during the solubilisation phase a') separate from the phase a), said solutions obtained respectively from the phases b) and a') being mixed together, before the concentration phase c). 12. The method as claimed in claim 1. characterised in that during the solubilisation phase a) a first portion of one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen, Phosphor and Potassium is dissolved, while a second portion of said soluble salts is dissolved during the solubilisation phase a') separate from the phase a), said solutions obtained respectively from the phases b) and a') being mixed together, before the concentration phase c). 13. The method as claimed in claim 1 , characterised in that after the phase b), one or more soluble salts containing the nutrients selected in the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu, B and Mo are dissolved directly in the solution. 14. The method as claimed in claim 1 , characterised in that after the phase b), one or more soluble salts containing the fertilising elements selected in the group consisting of Nitrogen, Phosphorus and Potassium are dissolved directly in the solution. 15. The method as claimed in claim 1 , characterised in that one or more soluble salts containing the nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu. B and Mo, are in part dissolved during the solubilisation phase and in part solubilised during the phase obtained after the separation phase b). 16. The method as claimed in claim 1 , characterised in that one or more soluble salts containing the fertilising elements selected from the group consisting of NPK, are in part dissolved during the solubilisation phase and in part solubilised during the phase obtained after the separation phase b). 17. The method as claimed in claim 1. characterised in that one or more soluble salts containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu. B and Mo are divided into three flows whereof respectively the first one is added to the solubilisation phase a), the second one is added to the solubilisation phase a') and the third one is solubilised directly to the solution obtained from phase b). 18. A method as claimed in claim 1 , characterised in that one or more soluble salts containing fertilising elements selected from the group consisting of NPK are divided into three flows whereof respectively the first one is added to the solubilisation phase a), the second one is added to the solubilisation phase a') and the third one is solubilised directly to the solution obtained from phase b). 19. A water soluble fertiliser in the form of granules or prills comprising as fertilising elements Nitrogen, Phosphorus and Potassium obtained according to a method comprising the following phases: a. solubilisation in water of salts containing the fertilising elements of Nitrogen, Phosphor, and Potassium to form a solution, said solution comprising a fraction of non soluble solids in suspension; b. separation from the solution obtained during the phase a) of the fraction of non soluble solids in suspension, thus obtaining a solution free of solids in suspension; c. concentrating the solution free of solids in suspension obtained from the phase b) until obtaining a solution: and d. cooling the solution obtained from the phase c) until obtaining granules or prills. 20. The fertiliser as claimed in claim 19, characterised in that it has a solubility in water of at least 90%o by weight. 21. The fertiliser as claimed in claim 19, characterised in that it has a solubility in water of at least 95% by weight. 22. The fertiliser as claimed in claim 19, characterised in that it has a solubility in water of at least 99% by weight. 23. The fertiliser as claimed in claim 19, characterised in that the granules or prills have a dimension lower than 7 mm. 24. The fertiliser as claimed in claim 19, characterised in that the granules or prills have a dimension lower than 4 mm. 25. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method in which, during the solubilisation phase a), also one or more soluble salts containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu, B and Mo are dissolved. 26. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method in which, during the solubilisation phase a), also one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen, Phosphorus and Potassium are dissolved. 27. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method which comprises a solubilisation phase a') separate from the phase a) during which one or more soluble salts containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn. Cu, B and Mo are dissolved and a mixing phase during which, before the concentration phase c), the solutions obtained respectively from the phase b) and from the phase a') are mixed together. 28. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method which comprises a phase a') separate from the phase a) during which one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen, Phosphorus and Potassium are dissolved and a mixing phase during which, before the concentration phase c), the solutions obtained respectively from the phase b) and from the phase a') are mixed together. 29. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method in which, during the solubilisation phase a) a first portion of one or more soluble salts containing nutrients selected from the group consisting of S, Ca, Mg, Fe, Mn, Zn, Cu, B and Mo is dissolved, while a second portion of said soluble salts is dissolved during the solubilisation phase a') separate from the phase a), said solutions obtained respectively from the phases b) and a') being mixed together, before the concentration phase c). 30. The fertiliser as claimed in claim 19, characterised in that it is obtained by a method in which, during the solubilisation phase a) a first portion of one or more soluble salts containing fertilising elements selected from the group consisting of Nitrogen, Phosphor and Potassium is dissolved, while a second portion of said soluble salts is dissolved during the solubilisation phase a') separate from the phase a), said solutions obtained respectively from the phases b) and a') being mixed together, before the concentration phase c). 31. Use of the fertiliser as claimed in claim 19 in the localised fertilisation- irrigation, in widespread fertilisation-irrigation, in leaf fertilisation-irrigation, in hydroponic fertilisation-irrigation or by means of a distribution on the soil followed by irrigation.

Inventors: SABATINI NICOLA, SABATINI, NICOLA
Applicants: S I S O SOCIETA IND SEQUESTRAN, SABATINI NICOLA, S.I.S.O. SOCIETA INDUSTRIA SEQUESTRANTI ORGANICI S.R.L., SABATINI, NICOLA
Application year: 2000
Main classification: C05G3
IPC codes: C05B7, C05G3