DE3816570A1 - Preparation of fertiliser mixtures urea/ammonium chloride and/or tetraurea anhydrite - Google Patents

Abstract

Preparation of fertilisers which contain urea adducts urea/ammonium chloride CO(NH2)2.NH4Cl and/or tetraurea anhydrite CaSO4.4CO(NH2)2 - to reduce or suppress primary damage to plants - by melting urea either - together with ammonium chloride while mixing in solid calcium sulphate - or together with calcium chloride and mixing in solid ammonium sulphate - or together with ammonium sulphate, if appropriate more ammonium chloride, and mixing in solid calcium sulphate at approximately 80 to 130@C and cooling the product mixtures in addition to, if appropriate, granulation and, if appropriate, crushing of the cooled products.

Description

The following proposal concerns the manufacture of in particular Urea adducts suitable for plant nutrition, namely

• - Urea ammonia NH₄Cl · CO (NH₂) ₂ and / or
• - Tetra-urea anhydrite CaSO₄ · 4 CO (NH₂) ₂

as well as their mixtures, which as Products are poor or preferably free of unbound urea.

According to the proposed process, urea is reacted with melted between 80 and 130 ° C, in the heat with the implementation required solids are stirred and - if necessary with grain formation like granulation - cooled or broken if necessary. According to the proposed invention Urea melted together either

• a) stirred with ammonium chloride NH₄Cl and then with calcium sulfate CaSO₄, preferably in a molar ratio of 4 urea CO (NH₂) ₂ with at least 4 ammonium chloride NH₄Cl and at least 1 calcium sulfate CaSO₄; in the the latter case arise with the consumption of the entire urea especially urea ammonia NH₄Cl · CO (NH₂) ₂, something besides Tetra-urea anhydrite CaSO₄ · 4 CO (NH₂) ₂ with excess NH₄Cl as well CaSO₄ or
• b) with calcium chloride CaCl₂ and then with ammonium sulfate (NH₄) ₂SO₄ stirred, preferably in a molar ratio of 4 urea with at least 2 CaCl₂ and at least 2 (NH₄) ₂SO₄; arise in the latter case using all of the urea, especially urea-ammonia, next to it tetra-urea anhydrite and an excess of NH₄Cl and CaSO₄, or
• c1) there are preferably at least 4 urea in a molar ratio 1 H₂O water and a maximum of 1 ammonium sulfate melted and stirred with at least 2 CaSO₄ calcium sulfate, with tetra-urea anhydrite and ammonium syngenite (NH₄) ₂SO₄ · CaSO₄ · H₂O, or
• c2) there are 4 urea in the molar ratio and at least 1 H₂O and maximum 1 ammonium sulfate + 2 NH₄Cl ammonium chloride melted and stirred with at least 2 CaSO₄, with tetra-urea anhydrite, urea-ammonia and ammonium syngenite arise, and

these product mixtures a) to c2) are finally cooled, optionally granulated and broken if necessary. The specified information and a) -c2) are due to the implementations shown:

If water is added or if the soil is moist, it is released temporarily Urea pre-bound to CaSO₄ · 4 CO (NH₂) ₂. In the example group c):

The latter ammonium syngenite is only a by-product and as slow-acting nitrogen fertilizer has become known (DE 35 18 369 + 35 29 867 + 35 29 868). It has now been found that this (with its relative low N content) when added or by released and not rebound urea is decomposed with water release after:

(d) (NH₄) ₂SO₄CaSO₄ · H₂O + 4 CO (NH₂) ₂ = CaSO₄ · 4 CO (NH₂) ₂ + (NH₄) ₂SO₄ + H₂O.

This is undesirable for storage reasons for a solid fertilizer but suppressed in the proposed compositions. On the other hand According to the invention, there is the possibility of starting the N action delayed (incubation period), which for thermodynamic reasons which grows according to proposals c2), c1) according to a) and b).

Plant fertilization with urea (46% by weight N) is in a temperate climate problematic because urea easily causes plant damage there leads, which can then no longer be compensated in the further course of vegetation are; these disadvantages have ammonium nitrate, for example containing fertilizers. One tried successfully, urea to condense with organic aldehydes and these products use as slow-acting stock fertilizer. Your manufacturing route is complex and therefore expensive. In another way they also tried by nitrification inhibitors developed for urea (e.g.  DE 33 22 726), an over-fertilization or low-damage vegetation course to achieve with urea fertilization. This was also previously expensive, so for temperate climates at least for the Large area N fertilization, the ammonium salts introduced, in particular Ammonium nitrate, standard fertilizers remained and not as urea Mass product.

The presented according to the method proposals described above Urea adducts and their mixtures - i.e. with urea ammonia NH₄Cl · CO (NH₂) ₂ and / or tetra-urea anhydrite CaSO₄ · CO (NH₂) ₂ - reduce or suppress the disturbing plant damage.

Another advantage is the extreme product safety of the urea adduct mixtures; they are non-combustible and not autothermally decomposable; they are also physiologically harmless. After all, they are In addition to urea, proposed feedstocks are light and inexpensive procurable, namely the CaSO₄ either as anhydrite or (Waste) gypsum that is reused to reduce environmental damage, or the CaCl₂, for example as a landfill product of the Solvay soda production; Ammonium sulfate is a compulsory product in large quantities well available for decades, and - if the ammonia, NH₄Cl, not according to one of the proposed alternatives in the process itself incurs - is particularly cheap in the Far East, for example obtainable. Taking into account the water balance and evaporation are the various components other than those already mentioned Hydrates can be used, such as calcium sulfate hemihydrate CaSO₄ · 0.5 H₂O or gypsum CaSO₄ · 2 H₂O or calcium chloride-di- or -hexa hydrate CaCl₂ · 2 or with 6 H₂O or mixtures thereof.

The display variants of the adduct mixtures are not described above. Representations at lower temperatures are used for the individual adducts and at the same time highly watery (or alcoholic at all) Medium described, tetra-urea anhydrite according to "Gmelin" Vol. 28, Ca Part B, 3rd delivery (1961), p. 779, last 12 lines and urea-ammonia in Russ. Journal Anorg. Chem. 16 (8) 1971, pp. 1206-09; Shulga et al. Bergman "Interaction Urea with Ammonium salts". At "Gmelin", l. c. P. 780 is a tetra-urea anhydrite representation in Z. 1-14 noticeably higher temperatures (approx. 150 ° C) with unsatisfactory yield and annoying by-products.  

The products according to the invention are easy to control technically and relatively low temperatures between 80 and 130 ° C can be set with intensive low-temperature kneading with partial evaporation of water within 5-8 minutes, while keeping biuret formation reasonably low. The external hardness of the cold products decreases from the glassy-hard Product (a) over (b) to the slightly chalky product group (c) from. The melt compositions chosen for alternative (c) correspond approximately to the determined ternary eutecticals between 110-120 ° C; Overheating of these melts, for example 140 ° C should be avoided with particular care, as in this ternary melting range is the boiling range in proportion little higher temperatures begins. The shaping area when cooling the melt-solid products for one intended grain shape - for example granulation or spraying - gets bigger from (a) to (c), so cheaper; at (a) the gel-like fresh pre-mash is glassy and immovable above 95 ° C and stiffens stubbornly; (b) is considerably wider manipulable and granulable; these properties during this Further processing also depend noticeably on the chosen Residual water content and the excess amount of CaSO₄.

Example 1 corresponds to variant a)

4 moles of urea (240 g) + 4 moles of ammonium chloride (214 g) are up to a temperature of 120 ° C melted in 5 minutes and with 1 mol of anhydrite (136 g) at 100-110 ° C for 6 minutes intensive and Low-temperature kneading, cooling and breaking. The product contained 18.8 wt .-% N-NH₂, 9.6 N-NH₄, 0.4 biuret and 9.1 CaO.

Example 2 corresponds to variant a)

4 moles of urea (240 g) + 4 moles of ammonium chloride (214 g) are up to a temperature of 120 ° C melted in 4 minutes and with 2 moles of finely ground anhydrite (272 g) at 100-120 ° C for 6 minutes kneaded, cooled and broken intensively for long periods without overheating. The product contained 15.0 wt .-% N-NH₂, 7.8 N-NH₄, 0.18 biuret and 15.0 CaO.  

Example 3 corresponds to variant b)

1 mole of calcium chloride tetrahydrate CaCl₂ · 4 H₂O (183 g, composed from 1/2 mol of CaCl₂ · 2 H₂O and CaCl₂ · 6 H₂O) with 2 mol Urea (120 g) melted together in 4 minutes to 105 ° C, with 2 moles of ammonium sulfate (264 g) stirred together and rising to 85 120 ° C vigorously stirred for 3 minutes under partial evaporation Water; the mash mixture loses 1.5 mol (27 g) of water, it is cooled and broken. The product contained 10.8% by weight N-NH₂, 10.5 N-NH₄, less than 0.1 biuret and 10.9 CaO.

Example 4 corresponds to variant c1)

4 moles of urea (240 g) are mixed with 2 moles of water (36 g) and 100 g Ammonium sulfate was brought to 119 ° C. in 6 minutes and melted together and with a finely ground mixture of 2 moles of calcium sulfate (Anhydrite 272 g) and 32 g ammonium sulfate (total use of ammonium sulfate 132 g = 1 mol) at 105 ° with an increase to 131 ° C for 6 minutes kneaded very intensively for a long time under the evaporation of 0.9 mol of water (16.4 g), cooled and broken. The product contained 16.7% by weight N-NH₂, 4.4 N-NH₄, 0.2 biuret, 16.7 CaO.

Example 5 corresponds to variant c2)

4 mol of urea (240 g) are mixed with 0.8 mol of ammonium sulfate (105.6 g), 2 moles of ammonium chloride (107 g) and 1.6 moles of water (28.8 g) in 7 minutes melted down to 110 ° C and with 1.3 mol of finely ground calcium sulfate (Anhydrite 176.8 g) while increasing the temperature to 115 ° C. The paste-like mixture is stirred for 4 minutes, it evaporates about 0.16 mol of water (2.9 g). The product is cooled and broken; the still formable ("waxy") cooling area lies between 95 and 70 ° C, in this the product is also easy to granulate. The end product contained 16.9% by weight of N-NH₂, 8.1 N-NH₄, 0.16 biuret and 10.5 CaO.

Claims (6)

1. Process for the preparation of urea-ammonia CO (NH₂) ₂ · NH₄Cl and / or tetra-urea anhydrite CaSO₄ · 4 CO (NH₂) ₂ containing solid fertilizer mixtures, characterized in that urea is melted at 80 to 130 ° C together with alternatively

• a) ammonia NH₄Cl with subsequent stirring of finely ground calcium sulfate CaSO₄ or
• b) calcium chloride CaCl₂ with subsequent stirring of finely ground ammonium sulfate (NH₄) ₂SO₄ or
• c) ammonium sulfate, optionally with further addition of ammonium chloride to the melt, followed by stirring in finely ground calcium sulfate

and that these still warm mixtures cooled and, if necessary to get broken. 2. The method according to claim 1, characterized in that the melt-stir-in solid mixtures during cooling granulated or sprayed. 3. The method according to claims 1 or 2, characterized in that the overall composition is chosen so that alternatively to 4 moles of urea
according to a) at least 4 moles of ammonium chloride and as stir-in solid at least 1 mole of CaSO₄ calcium sulfate or
according to b) at least 2 moles of CaCl₂ potassium chloride and at least 2 moles of ammonium sulfate as the stir-in solid or
according to c1) at most 1 mol of ammonium sulfate is contained in the melt and at least 2 mol of calcium sulfate CaSO₄ is stirred into this as a solid or
According to c2) at most 1 mole of ammonium sulfate and preferably additionally 2 moles of ammonium chloride are melted in and 1.3 or more moles of CaSO₄ calcium sulfate are stirred into this as a solid. 4. The method according to claims 1-3, characterized in that the production of the melts with little overheating and at short notice in preferably 5-8 minutes and the incorporation of the stirred-in solids during intensive kneading with little overheating and in the short term preferably takes place in 6-10 minutes. 5. The method according to claims 1-4, characterized in that as calcium chloride component CaCl₂ with 2 to 6 water of crystallization or their mixtures and / or as calcium sulfate component CaSO₄ with 0.5 to 2 water of crystallization, as solids with one Grinding or grain fineness smaller than 0.2 mm can be used and the melting or mashing in the heat is part of the Evaporate water.