Chemistry: fertilizers – Processes and products – Organic material-containing
Patent
1993-09-15
1995-04-25
Lander, Ferris
Chemistry: fertilizers
Processes and products
Organic material-containing
71 30, 426807, 564 32, C05C 900, C05B 300
Patent
active
054095166
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for the production of phospho-nitrogenous products whose P.sub.2 O.sub.5 is soluble in neutral ammonium citrate.
The invention also relates to the products obtained according to the process which can be used as fertilizers or to comprise products suitable for animal feed.
BACKGROUND OF THE INVENTION
The attack of tricalcium phosphate by acids, particularly nitric, sulfuric and phosphoric, adapted to product phosphate salts soluble in neutral ammonium citrate and if desired in water, have been for a long time used industrially in the production of fertilizers and phosphate products for animal feed.
Urea is also employed, on a large scale, as nitrogenous fertilizer. Because of the major position it occupies in most of the developing countries, it constitutes even today the world's principal source of nitrogen used for fertilization of soil. Urea also has uses in animal feed.
It has on the other hand been known for a long time (the first published papers on the subject dating from 1935) that sulfuric acid combines with urea and that the mono- and bi-urea sulfates obtained have the property of forming eutectics. Processes using compositions of this type, adapted to produce liquid nitrogenous fertilizers (U.S. Pat. No. 4,116,664 of Sep. 26, 1978 and U.S. Pat. No. 4,310,343 of Jan. 12, 1982) or to treat cellulosic materials (U.S. Pat. No. 4,818,269 of Apr. 4, 1989) have been recently described.
Compositions based on phosphate salts and urea are also known and used in the production of complex granulated fertilizers. They are generally obtained by mixture of urea and phosphated compounds of the superphosphate type, produced by the attack of natural phosphate with sulfuric and/or phosphoric acid. But the industrial production and use of these products is attended by numerous difficulties which have until now greatly limited their development.
These difficulties arise from the fact that urea, which is always found in these compositions essentially in the free state, has a strong tendency to decompose above 60.degree. C. (that is below the temperatures which are usually used to dry the fertilizers) liberating ammonia which causes the reversion of monocalcium phosphate to bicalcium phosphate. It has, on the other hand, the property of substituting itself for water in the hydrates of calcium sulfate and/or mono- and bicalcium phosphates present in superphosphates, liberating free water which promotes the deliquescence of the granules of fertilizer and their hardening into a mass.
Also the products produced by these processes are extremely difficult to dry. Their shelf lives are on the other hand very mediocre, which practically excludes the possibility of distributing them in bulk.
The document PI 7908335 describes a process for the production of phospho-nitrogenous products whose P.sub.2 O.sub.5 is substantially entirely soluble in neutral ammonium citrate and in which there remains no significant quantity of free urea, this latter being, for the most part, combined in a urea compound of calcium sulfate, in which tricalcium phosphate is reacted with a reagent obtained by mixing sulfuric acid and urea containing a quantity of water less than 10% by weight and preferably of the order of 5%.
There is thus produced a double decomposition reaction, in the course of which: to 90%) into monocalcium and urea phosphates, soluble in water and neutral ammonium citrate, and as to a substantially smaller portion (of the order of 5 to 15%) into bicalcium phosphate, perhaps combined with molecules of water and urea, soluble in neutral ammonium citrate; form tetra-urea calcium sulfate of the formula: CaSO.sub.4.4CO(NH.sub.2).sub.2.
Substantially all the P.sub.2 O.sub.5 contained in the final product is soluble in neutral ammonium citrate and a large proportion of this P.sub.2 O.sub.5, generally greater than 80%, is soluble in water.
In the presence of water, the ureates hydrolyze freeing the urea they contain. Also, when there are applied to the products according
REFERENCES:
patent: 2074880 (1937-03-01), Whittaker et al.
Achard Patrick
Ilbizian Pierre
Limousin Laurent
Neveu Bernard
Peudpiece Jean-Bernard
Grande Paroisse S.A.
Lander Ferris
Transvalor
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