DD159040C4 - METHOD FOR PRODUCING HEMICULTURAL CORNERS - Google Patents

Description

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Method of manufacture; of urea grains

field of use ^ he invention

The invention relates to a process for the preparation of urea grains.

The urea granules prepared according to the invention are mixed with Süperphospbat- or Tripelphosphatkörnern and f \ used as a fertilizer.

Characteristic of the known technical solutions

For the production of urea grains, various methods are known. One of these is prilling, among which a method is meant herein, with a virtually water-free urea melt (having a water content of Hoch ~ least O _t l to 0.3. '%) Versprühtwird top of a prilling tower in a highly rising air stream of ambient temperature, wherein the drops become firm. The so Sustainer "- requested prills have a maximum diameter of not much more than JSS 3 mm and are mechanically rather weak.

Urea grains having larger dimensions and better mechanical properties can be obtained by granulation of a nearly anhydrous urea melt in a drum granulator, e.g. B. by application of the "spherodizer" «technique as described in GB-PS 894.773, or in a Tcpfgranulator, z. 8, as described in US Pat. No. 4,008,064, or by granulation of an aqueous urea solution in a fluidized bed, for example as described in NL patent application 78 06213. In the process according to the last-mentioned publication, an aqueous urea solution containing a urea condensate is used.

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concentration of 70 wt * ~% to 99.9, preferably 85 to 96 _etc. wt, -%, in a fluidized bed of urea particles sprayed in the form of very fine drops Rait an average diameter of 20 to 120 microns at a temperature at which the water evaporates from the solution sprayed on the particles and urea solidifies on the particles to form granules of a desired size, which may be 25 mm or more. Because this process produces quite a lot of fly ash, especially if the urea solution used as starting material contains more than 5% by weight of water, in particular more than 10% by weight of water, the urea solution preferably becomes a crystallization retardant for the urea, in particular a water-soluble addition - or condensation product of formaldehyde and urea, added, whereby the Flugstaubbildung is almost completely suppressed · The presence of the crystallization retardant causes the grains in their construction plastic

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"so that by rolling and / or poking the structure mechanically strong, smooth and round Korner can arise." The grains thus obtained have a high breaking strength, a large. "Stossviderstand and a low tendency to fly dust formation by mutual friction, and also do not bake, even on prolonged storage, although urea naturally shows a strong tendency to cake.

Urea grains obtained according to one of the known methods can not be used for the preparation of heterogeneous binary and ternary fertilizer mixtures, such as N-P or N-P-K

Blends by bulk blending with the cheap superphosphate or triple phosphate because such urea granules are incompatible with these phosphates. Mixtures of such urea grains with superphosphate or Tripelphosphatkörnern flow to ··. 'some time under the formation of an ungrantbare and unusable porridge. '

According to a lecture by G. Hoffmeister and G.H. Megar during "The Fertilizer Industry Round Table" on November 6, 1975 in Washington D.C. • this incompatibility is due to a reaction according to the equation

Ca (H ₂ PO _{1 +} ) ₂ .H ₂ O + k C0 (NH ₂ ) ₂ -). Ca (H ₂ PO ₂ ) ₂ Λ C0 (NH ₂ ) ₂ + H ₃ O

- ^ caused.

By reacting 1 mole of monocalcium phosphate monohydrate, the major constituent of superphosphate and triple phosphate, with h moles of urea, a urea-monocycium phosphate adduct is formed leaving one mole of water free. Because the adduct is very soluble, it dissolves smoothly into the freed water to form a large volume of solution which wets the grains in the mixture, thereby increasing the speed of the reaction. So far, no commercially acceptable means have been found to make urea compatible with superphosphate or triple-phosphate. For bulk mixing with urea can

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Thus, almost only the expensive phosphate fertilizers Monoammoniumphosphaj: and Dianjmoniumphosphat be applied.

<* ίί - '

Object of the invention

The object of the invention is to provide a process for producing urea grains having extraordinary properties, for example compatibility with superphosphate and triple phosphate grains.

Explanation of the essence of the invention

The invention has for its object to make compatible by a suitable additive when prilling or granulating a urea melt or an aqueous urea solution, the urea grains with superphosphate and Tripelphosphatkörnern. , *

The invention relates to a process for the production of urea grains by prilling or granulating a urea melt or an aqueous urea solution, which process is characterized in that the urea melt or solution to be prilled or granulated comprises a supplement containing roagnesium oxide.

Surprisingly, it has now been found that the grains obtained according to the invention in various proportions are compatible with superphosphates and triple phosphate grains, whereby they are suitable for bulk mixing with these phosphate fertilizers. Mixtures of urea granules obtained according to the invention with superphosphate grains or triple phosphate granules which had been subjected to the "TVA Bottle Jest" at 27 ° C. were still present after 7 weeks

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dry, whereas analogous mixtures with urea granules not according to the invention were already completely liquefied after 3 days.

Further, it has been found that the presence of magnesium oxide in prilling or granulating a urea melt or solution results in the formation of the grains being smooth and avoids the formation of fly-ash, while also the urea granules obtained have a very high breaking strength and a very high breaking strength show apparent specific gravity. It is also very surprising that the urea grains obtained according to the invention do not cake together, even during long storage. '

The magnesium oxide can be applied as such (MgO) or in the form of fully calcined dolomite (MgO + CaO) or of selectively calcined dolomite (MgO + CaCO-). A favorable effect is already perceived with an additional amount, corresponding to 0.1 wt.% MgO, based on the urea in the melt or solution. Preferably, the additive is used in an amount of 0.5 to 2% by weight of MgO, based on the urea in the melt or solution. If desired, larger quantities can be used, but this offers no particular advantages. The additive may be added to the urea melt or solution in the form of a powder prior to prilling or granulation.

Preferably, the grains are cooled after their formation at 30 ⁰ C or a lower temperature ^ ζ. Β. with a stream of air, the moisture content of which is preferably reduced so that the grains do not absorb moisture from the cool air during cooling.

tr 6 -

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The invention also relates to compatible, heterogeneous synthetic fertilizer mixtures of urea grains obtained by applying the process of the invention to superphosphate or triphosphate grains and, if desired, one or more other granular fertilizers.

Except urea and superphosphate or triple phosphate is usually e £ h Kalidüngerstoff as KCl, recorded in the mixture thus segregation is avoided the mixture, the grain dimensions of the components to be mixed are to be matched with each other.

For further information on the preparation of fertilizer granules, reference is made to US Patent 3,130,225 for prilling, to US Patent 4,008,064 for granulation in a pot granulator, to GB Patent 894 * for granulation in a drum granulator. 773 and for granulation in a fluidized bed to the NL patent application 7806213 referenced.

Execution at s pi el . ·

The effect of the process according to the invention is shown in the following examples. The "TVA Bottle Test" referred to therein is for the determination or compatibility of urea grains with superphosphate and Tripelphosphatkörnern. In this experiment, the state of a mixture of the urea grains to be tested with superphosphate or Tripelphosphatkörnern, which was kept in a closed bottle of 120 cm at 27 ⁰ C, examined periodically. The perceived condition is represented as follows:

D W-I W-2 1 W-3 W ~ 4

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Condition of the mixture >

= dry, free flowing

«= Wet spots, but usable

= moist and reasonably sticky, but probably

useful

"= Thoroughly wet and sticky, useless a very wet, useless H = hard together, useless

The "bag trial" mentioned in the examples determined the tendency to cake the tested grains. In this experiment, the urea grains were packed in bags of 35 kg, which were stored under a weight of 1000 kg at 27 ⁰ C. After one month, the average number of chunks per sack was determined and the middle half of the chunks was measured. By hardness is meant here the force in kg, exerted by a dynamometer, to let fall apart a Brocken

of 7x7x5 cm.

The mentioned in the examples, crystal growth inhibitors F 80 is a commercially available under the name "Formurea 80", between -20 ⁰ C and +40 ⁰ C stable, clear viscous liquid which according to analysis per 100 parts by weight about 20 parts by weight Water, about 23 parts by weight of urea and about 57 parts by weight of formaldehyde, of which amount of formaldehyde about

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55% is bound as Trimethylolharnstoff and the rest in nicht. · -> ° -i "bound state is present.

Example I ·. , ,

Experiments were carried out, wherein an aqueous urea solution without a known crystallization delay (F 80) and with this and with magnesium oxide as crystallisationsverzogerer was sprayed in a Fliessebtt of urea particles. The granulation conditions and the physical properties of the obtained grains are mentioned in Table A. · ·

4 **

m. 9 -

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"TAB E_L LEA

None crystallisation agent none \% F80 0.6% MgO \% MgO

Granulation conditions .

urea solution

- Concentration, wt%. 9 ^, 6 94.5 9U.5 9U, 5 - temperature, C 130 130 130 130 Yield, kg / hour  '28o -280 280 280 Injizierluft Yield, Nm / hour '130 130. 130 130 - temperature, C · 1UO 1U0 IUO 1U0 fluidizing ' - Yield, Hm / hour 850 850 85O 850 - temperature, C U5 6k 5U 58 - bed temperature, C 108 105 10U, 10U product features 3 - apparent density, g / cm 1.23 1.26 1.30 1.31 Breaking strength 0'2.5 mm, kg 2.1 2.8 U, 3 - Fog dust, g / kg 5, U <0.1 0.1 <0.1 - try things ¹ - chunks, % 100 10 0 0 - Hardness, kg 22 <E, 1 0 0 - TVA Bottle Test with superphosphate 50/50 after 1 day W-2 W-2 ID D after 3 days W-U ' W-U. D D after 7 days W-U W-U D D after lU days W-U W-U W-1 D after 21 days W-U w-U W-1 D after 50 days W-U W-U , W-I D with Tripelphosphat 50/50 after 1 day * ^w " ² W-2 D D after 3 days w-U w-U D D after 7 days W-U WU ' D D after Tk days W-U W-U W-1 D after 21 days W-U W-U W-1 D after 50 days W-U W-U W-1 D

--10 τ ·

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Example II ., ..,,

A series of experiments was carried out in an analogous manner as described in Example I, but with selectively calcined dolomite and with fully calcined dolomite as crystallization retardant in place of magnesium oxide. The granulation conditions and the physical properties of the obtained grains are mentioned in Table B.

selectively calcined 2.2 dolomite 3% completely calcined T, 5 * dolomite Crystal growth none 100 3% granulation 13 95.5 urea solution 9 & 5 130 - Concentration, wt%. 9 ^ 5 130 220 95.5 95.5 - temperature, C 130 220 130 130 Yield, kg / hour 200 130 220 · 220 Injizierluft 130 IU9 Yield, Nm / hour 130 13U ₁ 130 130 - temperature, C 1UO 850 150 IU9 fluidizing 85O ' 66 Yield, Nm / hour 850 75 92 850 85O - temperature, ⁰ C 58 '98. 53 57 - bed temperature, ° C 100 1.31 95 9k . product features 1.29 3.9 - apparent density, g / cm 1.22 u, o 0 1.29 1.32 Breaking strength 0 2,5mm, kg 1,9 0 3.7 3, U - Fog dust, g / kg 7 .0 0 - Sack attempt 9 - Brocken, % 10 23 - hardness, ke 2 2

«TVA Bottle Test

to

with superphosphate 3. days 1U days lh days

50/50 liquefied useful usable

after 1U days 1U days

Usable liquefied useful for 3 days

with triple phosphate 5Ο / 5Ο

more than more than

60 days 60 days

useful usable

more than more than

βθ days 60 days-

useful usable

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Example III

A virtually water-free urea melt without addition and with the addition of magnesium oxide was sprayed in a prilling tower in a high-rising air flow from ambient temperature.

The physical properties of the obtained prills are mentioned in Table C.

additive

TABLE ^ no

0.72 # MgO $ 0.95 MgO

product features

- apparent density, g / cm

- Breaking strength, 0 2.5 ma, kg. - Sack attempt

- Brocken, % '

- Hardness, kg

- TVA Bottle Test

with triple phosphate

1.30 1.32 1.33 g - 0.5 ^ + 1,0U 1.16 100 0 0 9 0 0 after 3 days more than more than liquefied 60 days 6o days useful useful after 3 days more than more than liquefied 60 days 60 days useful useful

Example IV

A urea melt to which magnesium oxide had been added was granulated in a rotating horizontal granulation drum having a diameter of 90 cm and a width of βθ cm. The drum was provided on the inner wall with eight at equal intervals arranged longitudinal strips of 3.5 x SO cm. The Drs Jizahl was. 15; Revolutions / minute. The drum was filled with 60 kg of urea granules having an average diameter of 1.8 mm and a temperature of 80 ° C.

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By means of two hydraulic sprayers 6o kg of aqueous urea melt (99.8 wt% urea.), 0.6 wt% MgO was added at a temperature of 1UO -. 1 ^ 5 C in an amount of about 100 kg / Hour in the rotating drum over the like a rain veil from the longitudinal stripes falling grains sprayed. The granulation took place at 110 ⁰ C.

At the end of the test the granules were cooled to about 3O ⁰ C and sieved. The product granules had good roundness and a smooth surface. The apparent density was 1.288 g / cm.sup.2 and the breaking strength 0.25 mm was 3.5 kg. The fly dust formation was 3 ^ 9 g / kg. The grains showed almost no tendency to cake. Superphosphate (50/50) and tripel phosphate (50/50) blends were useful for more than 60 days. The sieve analysis of the product was as follows:

> U, 00 mm: 7

U, 00 - 2.5 mm-: U6%

2.5 - 2.0 mm: · 29 * <2.0 mm: 8%

average diameter: 3.0 mm

Claims (4)

->! E rf indunqsansprueh 1. A process for the deproteinization of urea grains by prilling or granulating a urea feces or an aqueous urea solution _y characterized in that the urea melt or solution to be prilled or granulated contains a magnesium oxide-containing additive. " 2. The method according to item 1, characterized in that the urea melt or solution MgO as such or in the form of selectively or completely kal ~  Containing calcined dolomite * O ' 3 »Process according to items 1 to 2, characterized in that the additional amount corresponds to at least 0.1% by weight of MgO, relative to the urea in the melt or solution.« 4. The method according to points 1 to 3, characterized in that the additional amount of 0.5 to 2 wt .-% MgO, based on the urea in the melt or solution corresponds to «.