UREA-CONTAINING FERTILIZERS AND PROCESS FOR PRODUCTION THEREOF

Abstract

A particulate, urea-containing composition and use of an additive for producing a particulate, urea-containing composition and methods of producing a particulate, urea-containing composition.

Claims

1-18. (canceled)

19. A particulate composition comprising: (i) urea; and an additive comprising component (ii) and one or both of components (iii) and (vii): (ii) one of a combination of polyethyleneimine and polyvinyl alcohol and a combination of polyethyleneimine and polyvinylamine; (iii) at least one aliphatic C.sub.2-C.sub.8 dialdehyde; (vii) at least one compound selected from the group of aliphatic dicarboxylic acids, their salts and anhydrides, aliphatic tricarboxylic acids, their salts and anhydrides, aromatic dicarboxylic acids, their salts and anhydrides, and aldehydic acids, their salts and anhydrides, and an adjuvant comprising one or more of components (iv) to (v): (iv) sulfur; (v) ammonium sulfate; wherein the weight fraction of component (i) is greater than 50 wt % and the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 1 wt % and the weight fraction of the sum of components (iv) and (v) in the composition is less than 50 wt % and the weight ratio of components (ii) and (iii) or the weight ratio of components (ii) and (vii) is in the range from 1:20 to 20:1.

20. The particulate composition of claim 19 wherein component (ii) is a combination of polyethyleneimine and polyvinylamine, component (iii) is one or both of ethanedial and glutaraldehyde; and component (vii) is selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride, glyoxylic acid and salts thereof.

21. The particulate composition of claim 19 wherein the polyethyleneimine of component (ii) has a molecular weight in the range of 500-2,000,000 Da.

22. The particulate composition of claim 19 wherein component (ii) includes polyvinylamine having a molecular weight in the range of 500-1,000,000 Da.

23. The particulate composition of claim 19 wherein the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 0.5 wt %.

24. The particulate composition of claim 19 wherein the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 0.4 wt %.

25. The particulate composition of claim 19 wherein the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 0.3 wt %.

26. The particulate composition of claim 19 wherein the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 0.25 wt %.

27. A method for producing a particulate composition comprising urea, comprising the steps of: providing a urea-containing solution; and granulating or prilling the urea-containing solution with addition of one or both of an additive comprising component (ii) and one or both of components (iii) and (vii): (ii) one of a combination of polyethyleneimine and polyvinyl alcohol and a combination of polyethyleneimine and polyvinylamine; (iii) at least one aliphatic C.sub.2-C.sub.8 dialdehyde; (vii) at least one compound selected from the group of aliphatic dicarboxylic acids, their salts and anhydrides, aliphatic tricarboxylic acids, their salts and anhydrides, aromatic dicarboxylic acids, their salts and anhydrides, and aldehydic acids, their salts and anhydrides, and an adjuvant comprising one or more of components (iv) to (v): (iv) sulfur; (v) ammonium sulfate.

28. The method of claim 27 wherein the urea content of the solution is greater than 10 wt %.

29. The method of claim 27 wherein the urea content of the solution is greater than 50 wt %.

30. The method of claim 27 wherein said granulating is performed by fluidized bed granulation, comprising the steps of: providing urea-containing nuclei; fluidizing the urea-containing nuclei; and spraying the urea-containing solution onto the nuclei, using one or both of the additive and the adjuvant.

31. The method of claim 27 wherein the temperature of the urea-containing solution is greater than 120 C.

32. The method of claim 27 wherein the temperature of the urea-containing solution is greater than 125 C.

33. The method of claim 27 wherein the temperature of the urea-containing solution is greater than 130 C.

34. The method as claimed in claim 27, further comprising: separating the particulate urea composition after its production into three fractions, wherein one fraction (F1) contains particles having the desired target size, one fraction (F2) contains particles having a size above the desired target size, and one fraction (F3) contains particles having a size below the desired target size.

35. The method of claim 27 further comprising: wet scrubbing.

36. A fertilizer comprising: a particulate urea composition comprising: (i) urea; and an additive comprising component (ii) and one or both of components (iii) and (vii): (ii) one of a combination of polyethyleneimine and polyvinyl alcohol and a combination of polyethyleneimine and polyvinylamine; (iii) at least one aliphatic C.sub.2-C.sub.8 dialdehyde; (vii) at least one compound selected from the group of aliphatic dicarboxylic acids, their salts and anhydrides, aliphatic tricarboxylic acids, their salts and anhydrides, aromatic dicarboxylic acids, their salts and anhydrides, and aldehydic acids, their salts and anhydrides, and an adjuvant comprising one or more of components (iv) to (v): (iv) sulfur; (v) ammonium sulfate; wherein the weight fraction of component (i) is greater than 50 wt % and the weight fraction of the sum of components (ii), (iii) and (vii) in the composition is less than 1 wt % and the weight fraction of the sum of components (iv) and (v) in the composition is less than 50 wt % and the weight ratio of components (ii) and (iii) or the weight ratio of components (ii) and (vii) is in the range from 1:20 to 20:1.

Description

EXAMPLES

Example 1

[0137] In an experimental plant, urea was granulated with 7 wt % of elemental sulfur in a fluidized bed granulator comprising a cylindrical fluidized bed with a diameter of 40 cm at a temperature of around 108 C. The fluidized bed ended on the underside with a perforated plate whose holes had a diameter of 2.0 mm. With a superficial velocity of around 2 m/s, the fluidizing air flowed into the fluidized bed. An overflow was placed 10 cm above the bottom plate on the side wall of the bed. A defined quantity (around 45 kg) of particles or granules having a narrow size distribution was then introduced as granulating nuclei into the column of the granulator. The bed with the nuclei (around 50 cm deep) was fluidized with hot air at a temperature of around 100 C., and the addition of 96 to 97 wt % strength urea solution with a temperature of around 135 C. was commenced as soon as the bed had attained the temperature of around 108 C. envisaged for the run. From a supply tank, the solution, consisting of urea and sulfur with a water content of 3-4 wt %, was then supplied at a rate of 350 kg/h via a spraying nozzle, which was operated at a temperature of around 140 C. with air supplied at a rate of 240 kg/h, into the fluidized bed granulator. The granulating additives used according to table 1 below were then mixed at around 135 C. with the solution consisting of urea and sulfur. Solids were removed from the fluidized bed via an outlet at regular intervals of 5 minutes, in order to maintain a largely constant bed height. The samples of the solids thus removed were then each sieved for determination of their size distribution. No solids were returned to the fluidized bed granulator. The duration per batch was in each case around 30 minutes. After this time had elapsed, the supply was interrupted, and the granules were cooled to around 100 C., removed from the fluidized bed granulator and sieved for separation into the various fractions. The fraction with the desired size distribution was then cooled to around 60 C. for analysis of its product properties. All fractions were weighed to determine the growth rate of the granules. Furthermore, the dust from the bag filters of the air removal apparatus was also collected and weighed.

[0138] In accordance with the procedure described above, comparative granulation experiments as well, without addition of additive and also with polyvinylamine (PVA), a polyvinylamine/polyethyleneimine mixture or a standard additive (urea-formaldehyde additive UF80), were carried out and the granules obtained in each case were worked up accordingly and analyzed.

[0139] Table 1 below shows the corresponding assessment of the granules in relation to dusting, compressive strength, density and caking. The dusting sensitivity, which is likewise reported, is the result of a visual assessment of captured dust from a small fluidized bed condenser. The scale used for the evaluation of the granules obtained is shown in table 1 b.

[0140] Suitable analytical methods for the product properties are known to the skilled person. Reference may be made, for example, to ISO 3944 or IFDC S-112 for determining the bulk density, to IFDC S-116 for determining the dusting, to IFDC S-115 for determining the compressive strength, and to IFDC S-106 for determining the caking, the IFDC techniques being those of the International Fertilizer Development Center, Muscle Shoals, Ala., USA.

TABLE-US-00001 TABLE 1 Additive wt % PVA/PEI/ PVA/PEI/ PVA/PEI/ PVA/PEI/ PVA/PEI PVAl CA PVAl/CA CA UF80 88/12 44/6/50 34.5/3.5/62 17.2/1.8/50/31 80/10/10 Inventive (E)/ V V E E E E E comparative (V) Amount added 0 3000 1000 2000 2000 2000 1000 mg/kg Parameter good means Dust in low 5 2 2 2 1 2 2 granulator filter Dusting cooling low 5 2 2 2 1 2 2 Caking % none 3 1 1 1 1 1 1 Lump hardness FF* 3 1 1 1 1 1 1 Compressive high 4 2 2 2 1 2 2 strength Bulk density high 3 1 1 2 1 1 1 (loose) Assessment 23 9 9 10 6 9 9 (unweighted) PVA: polyvinylamine PEI: polyethyleneimine PVAl polyvinyl alcohol CA citric acid FF free flowing

TABLE-US-00002 TABLE 2 Dust in the Compres- Bulk Hard- filter Dust sive density Caking ness Scale (%) cooling strength kg (g/l) (%) (kg) 1 0-4 0 >3.5 >675 .sup.0 none 2 >4-6 1 >3.0-3.5 675-665 0-10 slight 3 >6-8 2 >2.5-3.0 <665-655 11-20 moderate 4 >8-10 2-3 >2.0-2.5 <655-645 21-30 hard 5 >10 3 <2.0 <645 >30

Example 2

[0141] In accordance with the procedure described in example 1, the effect was determined of a granulating additive of the invention composed of citric acid in various dosages and mixtures of polyethyleneiminine and polyvinylamine. In this case the citric acid was supplied as a mixture of polyethyleneiminine/polyvinylamine and in dosed form to the stream of urea and sulfur that was supplied to the nozzle, prior to spraying. The resulting solution, consisting of urea and sulfur with a water content of 3 wt %, was then supplied at a rate of 350 kg/h at a temperature of 132 C., and working up took place as described in example 1. A corresponding comparative experiment with formaldehyde was likewise performed.

[0142] Table 1 shows in each case the fraction of dust in the fluidized bed granulator, and also gives the corresponding assessment of the granules of example 2.

Example 3

[0143] In accordance with the procedure described in example 1, the effect was determined of granulating additives of the invention, consisting of a mixture of 500 mg/kg polyethyleneiminine and polyvinylamine (40 wt %/60 wt %, based in each case on the mixture of polyethyleneimine and polyvinylamine) with oxalic acid, citric acid, succinic acid, phthalic acid, phthalic anhydride, glutaraldehyde and also glyoxylic acid, on the granulation of urea and ammonium sulfate. Oxalic acid, citric acid, succinic acid, phthalic acid, phthalic anhydride and glutaraldehyde were each added to the urea reservoir, and the glyoxylic acid and also the mixture of polyethyleneiminine and polyvinylamine were each added, prior to spraying, to the solution consisting of urea and ammonium sulfate that was supplied to the nozzle. Here again, the solution thus obtained with a water content of 3 wt % was then supplied at a rate of 350 kg/h at a temperature of 132 C., and working up took place as described in example 1. A corresponding comparative experiment with formaldehyde was likewise performed.

TABLE-US-00003 Compressive Inventive (E)/ Dosage strength Dusting comparative (V) (mg/kg) (in kg) (in %) No additive V 0 2.26 10.85 Formaldehyde V 4500 3.75 3.90 Oxalic acid E 1000 4.48 2.81 Citric acid E 1000 4.05 4.44 Succinic acid E 1000 3.63 3.70 Phthalic acid E 1000 3.84 3.70 Phthalic anhydride E 1000 4.72 2.48 Glutaraldehyde E 1000 3.71 3.65 Glyoxylic acid E 1500 5.07 2.74

[0144] The investigations of the granules obtained according to examples 1-3 showed that both dusting and the properties of the granules (compressive strength, tendency toward caking) improved when the additives of the invention were added. The result was comparable with or even better than the results obtained when using formaldehyde, while requiring substantially smaller quantities of additive.