DD145371A1 - METHOD FOR THE PRODUCTION OF GRANULATED UREA - Google Patents

Abstract

The invention relates to a process for the production of granulated urea with improved Quality parameters, especially with increased mechanical stability of the urea granules. That will achieved by the addition of iron hydroxide alone or in a binary or ternary mixture with Magnesium hydroxide, red mud, metakaolin, polyvinyl alcohol and / or technical fatty amine mixtures to the urea solution or melt before pricking. The effect of the measure according to the invention is due to a change in the strength affecting internal structure of the urea prills.

Description

Process for the production of granulated urea Field of application of the invention

The invention relates to a process for the production of granulated, storable and free-flowing urea with improved microstructural and stability properties, which is used in agriculture or as a chemical raw material.

Characteristic of known technical solutions Increasing the granular strength of urea is necessary in order to minimize or completely avoid fragments and abrasion particles which arise during transport and storage, especially from loose, granulated urea. Granule fragments and dust are known to favor the hardening of the urea loosely stored under varying atmospheric conditions, thereby adversely affecting its applicability, especially as a high-grade nitrogen fertilizer.

It is known that the cause of these hardening phenomena are crystal bridges which, with variations in the atmospheric conditions, develop particularly frequently in urea granules with high fines. ^{In order to} prevent this crystal bridge formation, various measures have been proposed, which are mostly subordinate to the granulation process.

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Applying a powdered layer of an inert inorganic material (e.g., kieselguhr, kaolin) to the fertilizer granules

(Brit. Pat. 1 168 106J

'Fr. Pat. 1 580 619;

US Pat. 3,192,031)

- Spraying the granules with aqueous dispersions of different clays

(DE-AS 1 115 747)

Modification of the Gjanalien surface by means of suitable adsorbable organic compounds, e.g. Alkylaraine,

(DE-AS 1 075 642;

Brit. Pat. 876,675)

It is also known that the transport and storage properties as well as the increase in the stability of urea prills can also be improved by modifying the starting melt, for example by adding activated inorganic compounds such as clay minerals or clay mineral mixtures (DD-WP 123944) or by 2 _U addition of organic substances, such as polyvinyl alcohols, polyvinylamines or polyacrylamide (DD-WP 131062.) To urea melt.

Disadvantages of the previously proposed measures for improving the quality of the urea granules are either in the price of the modifier or z.T. considerable technical effort, e.g. in connection with the application of a powder layer, with which superficial melting of the granules particles or with the activation of clay minerals or clay mineral mixtures is required »

In other known additives, such as e.g. Ammonium sulfate and various inorganic phosphates, the quality-enhancing effects are not sufficient.

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Object of the invention

The aim of the invention is the preparation of a urea by the prilling process, which is characterized by increased stability of the individual granules with good transport and storage behavior. The method according to the invention does not require expensive technological measures.

Explanation of the We sens the invention

The object of the invention is to Harnst offgranalien ristallgefüge verbessertem- with ^K and, as a result of increased mechanical stability thereby establish that the urea solution prior to the evaporation, or directly to the urea melt prior to prilling more effective additives are added.

It has been found that urea granules with improved mechanical stability and thus improved handling and storage behavior arise when added to the urea solution prior to evaporation or urea melt prior to spraying ferric hydroxide alone or together with various inorganic and / or organic compounds as a binary or ternary mixture becomes. As inorganic and organic compounds, which are used together with iron hydroxide individually or in mixtures as additives to the urea solution or melt according to the invention, are suitable magnesium hydroxide, red mud as a technical product of various oxides, metakaolin, polyvinyl alcohol and technical products of various fatty amines.

The hydroxides of iron and magnesium may also be generated by the reaction of their water-soluble salts with the free ammonia in the urea solution or melt. The ^G ehalt of these additives in the urea to 0.01 to 0.6 wt .- ^, preferably 0.1 to: _0? 2 Gew .- ^ amount, under these conditions arise in Verprillen urea granules whose individual crystal regions are arranged irregularly and largely interlocked with each other. The iron content leads to a weak brown coloration of the urea granules. The erfinäungsgemäßen additives are added to achieve the desired effect together or sequentially added to the urea and secured a homogeneous distribution in the melt before the spoil »

Out of gear is pi el β example 1

Prevent a urea melt (14O ° C) from mixing 0.2% by weight powdered iron hydroxide. This melt is sprayed into a granulate with diameters between 0.5 and 2.5 mm. The prills show in the thin section "image under the microscope a far-reaching Vexzahnung the irregularly arranged crystal areas.

Static Prick Strength (kp / Prill). To determine this, the breaking load of the 2.00 mm prills was determined on a consistener from 15 individual determinations per sample. Found value: 0.98 kp Comparison value of a urea sample without additives

0.80 kp

Dynamic Prillstrength. (Shatter test 00) The percentage fraction of the residue of the prill fraction is determined to be 1.6 to 2.0 mm after an impact test (at 2 atm carrier gas flow).

Found value: 80 % comparative value of a urea sample without additives:

72 ί

Beispiel.2

To a 75% urea solution at 80 ⁰ C concentrated aqueous Eisenensialfatlösung be added with stirring. The iron content is adjusted to 0.1 to 0.2% by weight, based on the amount of urea. After evaporating the solution in vacuo, the ^K is ristallbrei melted and verprillt. The examinations of the resulting prills are analogous to Example Static Prill Strength: 1.06 kp Shatter Test Test Condition: 89 ° h

Example 3

Molten urea 0.1 analogously to Example 1 by weight. -4> iron hydroxide powder and 0.1 g of ₆ w .- ^ ϊ / iagnesiumhydroxid powder was added and after thorough mixing the melt verprlllt *

Static Prick Strength: 1.08 kp Shatter Test Residue: 91 ^

Example 4 . ·

0.1% by weight of iron hydroxide and 0.1% by weight of metakaolin are added to the urea melt. After intensive mixing, the melt is sprayed.

Static Jrillfestigkeit: 1.11 kp

Shatter test residue: 90.5 ^

Example 5

In a urea melt, 0.1% by weight of iron hydroxide and 0.1 μg of polyvinyl alcohol are homogeneously distributed and the melt is subsequently sprayed.

Static Prick Resistance: 1.21 kp Shatter Test Residue: 92 #

Example 6

Analogously to Example 5, a urea melt is sprayed in the previously 0.1 wt .- ^ iron hydroxide and 0.05 wt .- # Sfamin T (fatty amine technical mixture) are homogeneously distributed. Static Prick Strength: ^ 0.98 kp Shatter Test Backlog: 78 <$>

Example 7

A 0.1 wt .- # hydroxide, 0.05 wt .- ^ polyvinyl alcohol and 0.1 Gevi _e - # metakaolin Harnst offset offs is chmelze verprillt after homogeneous mixing of the additives.

Static Prill Stability: 1.28 kp

Shade test residue: 93 #

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Claims (1)

Inventory proposal A process for producing granulated, storable, and free-flowing urea with improved structural and stability properties of the single prills, characterized in that the urea solution prior to evaporation or the urea soy before spraying ferric hydroxide alone or in a binary or ternary mixture with various inorganic and / or organic Compounds iäie magnesium hydroxide, red mud as a technical product of various oxides, metakaolin, polyvinyl alcohol and / or technical Fettamingemisehe, wherein the hydroxides of iron and magnesium can also be produced by reaction of their water-soluble salts with the free ammonia in the urea solution or melt, in an amount of from 0.01 to 0.6% by weight, preferably 0.1 to 0.2% by weight, of S ₁ added to the urea is added.