DD145370A1 - 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. This will ; achieved by adding small amounts of cation-active polymer electrolytes or mixtures thereof with various inorganic and / or organic substances. Suitable polymer electrolytes are technical Condensation products of dicyandiamide, formaldehyde, ammonia and ammonium sulfate or melamine-forrehyde condensation products. Suitable inorganic and organic substances in admixture with used in the polymer electrolyte are magnesium, aluminum or iron hydroxide, Red mud, metakaolin, polyvinyl alcohol and technical products of various fatty amines. The additives are added to the urea solution before evaporation or. to the urea melt before Spraying added. The effect of the measure according to the invention is based on a change in the Strength-influencing internal structure of urea prills.

Description

Process for the production of granulated urea

Applicability 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, is used in agriculture or as a chemical raw material.

Characteristics of the known technical Lö sun conditions

The increase in the granule strength of urea is necessary to keep as low as possible during transport and storage, especially of loose, granular urea resulting debris and abrasion su or completely avoid su. 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 this hardening phenomena are crystal bridges that very frequently emerge in response to variations in atmospheric conditions in urea granules with high fines · ² for preventing this Kristallbxückenbildung been proposed various measures that ß the Granulationspro ze mostly na oily assigns are.

- Applying a powdered. Layer of inert inorganic material (e.g., kieselguhr, kaolin) on the

Fertilizer granules. '

(Brit. Pat., 1 168 106 ;.

Pat. 1 580 619;

US Pat. 3 192 031)

- Spraying granules with aqueous dispersions of different clays

(DE-AS 1 115 747)

- modification of the granule surface by means of suitable adsorbing bare organic compounds, for example _e alkylamines (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, e.g. by adding activated inorganic compounds, such as clay minerals or clay mineral mixtures (DD-Y / P 123944) or by adding organic substances, such as polyvinyl alcohols, polyvinylamines or polyacrylamide (DD-WP 131062) to the urea ohmel.

Disadvantages of the previously proposed measures to improve the quality of urea granules are either on the price of the modifier or in some cases ₀ considerable technical effort, which for example is required in connection with the application of a Pudexschicht, with the superficial melting of the granules or with the activation of clay minerals or Tonmineralgeraischen ·

In other known additives, such as, for example, ammonium sulfate and various inorganic phosphates, the quality-improving effects are not sufficient.

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.

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Darl eg the nature of the invention

The object of the invention is to produce urea granules with improved crystal structure and resulting with increased mechanical stability, characterized in that the urea solution melted before evaporating or directly from the Harnst off before their Versprühung more effective ² added additives ·

It has been found that urea granules with improved mechanical stability and thus improved handling and storage life result when the urea solution before evaporation or the urea melt before spraying cationic polymer electrolysis or mixtures thereof with various inorganic and / or organic substances are added and then in a known manner, the processing of the thus modified melt is carried out.

As polymer electrolytes which are added to the urea solution or melt, condensation products of dicyandiamide, ammonia, ammonium sulfate and formaldehyde or melamine-foraldehyde condensation products are suitable.

Suitable inorganic and organic compounds to be incorporated with these condensation products of the urea solution or melt are mixtures of magnesium, aluminum or iron hydroxide, red mud as a technical product of various oxides, metakaolin, polyvinyl alcohol and technical products of various fatty amines. Particularly advantageous is the ² ugabe of concentrated aqueous magnesium, aluminum or iron salt solutions to the urea solution or urea melt to as the respective hydroxides are formed in very finely dispersed form with the free ammonia present therein. As a result, the modification is better suited to the structure in the urea granules which forms on solidification from the molten state, but the technological design of the inventive solution is also simplified.

The content of these additives in the urea to 0.01 wt "to 0.6 wt .- #, preferably 0.1" to 0.2. Amounted -4> ". Under these conditions arise during Yerprillen urea granules whose individual crystal Irber oak irregularly arranged and interlocked.

The condensation products used according to the invention are added to the urea to achieve the desired effect alone or together with one or two of the specified additives and distributed homogeneously in the urea melt prior to dissolution.

EXAMPLES

example 1

In a Haxnstoffschmelze (140 ⁰ C) are added with stirring 0.1. -Ί> copper-free Wofafix S powder (condensate! Onsprodukt of dicyandiamide, formaldehyde, ammonia and ammonium sulphate) was added and homogeneously mixed "This melt is to granules with Prilldurchmesaern sprayed between 0.5 and 2.5 mm. This product remains free after six changes of climate in alternating wet-cold (90 Io relative humidity and 15 ⁰ C) and dry-warm (30 ° h relative humidity and 50 ⁰ C) conditions even in higher beds (4 to 6 m), shows no signs of caking over months and has better microstructural properties as well as increased strengths in the single prills.

The prills show in the thin-section image under the microscope a largely interlocking of the irregularly arranged crystal regions,

The mean static endurance (breaking load in kp / prill) was 0.845 kp for 2.0 mra prills (comparative value for prills without additives 0.800 kp). The determination of the mean dynamic Prillfestigkeit (Shatter test) gave a value of 82 #. In this case, the percentage fraction of the residue of the Prillfraction 1.6 to 2.0 mm after an impact test at 2 at-carrier gas flow was determined (Yergleichswert for prills without additives 72 #). ·

14-4f

Example 2

A 75 ^ urea solution are added at 80 ⁰ C 0.1. Copper-free Wofafix-S-powder is added (condensation product of dicyandiamide, formaldehyde, ammonia and ammonium sulphate) (based on the urea content in the solution) and homogeneously distributed in the E solution. This solution is concentrated in vacuo to dryness, the crystals are melted and sprayed. The investigations of the resulting prills were carried out analogously to Example 1:

Static Prill Resistance: 0.890 kp Shatter Test Residue: 83 #

Example 3

Analogously to Example 1, a urea melt (14O ° C) is heated to 60 ⁰ C heated about 50 #ige Wofafix solution (condensation product of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) added, the amount of Y / ofafix S is so dimensioned in that, based on urea, a wofafix content of about 0.1 gevn is established.

The investigation of the urea prills showed a stability behavior analogous to Example 1.

Example 4

0.05% by weight of Wofafix® S-ulver (condensation product of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) and 0.1% by weight of finely powdered magnesium hydroxide are added to a urea melt and, after good mixing, the melt is sprayed.

The prills show in the thin section image under the microscope according to Example 1, a toothing of the highly disordered crystal regions with individual Mg (OH) "chilies sen. Static Prill Resistance: 0.92 kp Shatter Test Residue: 88 #.

Example 5.

With 0 _s ^ o O5 Gbyu- Piafol (melamine-formaldehyde Kondensa onsprodukt ti) and 0.1 wt. -4> finely powdered Rotschlammpulver offset Harnst off melt is verprillt. The weakly colored

Urea prills show the following strength values: Static Prill Strength: 1.12 kp Shatter Test Result: 87 ^.

Example 6

Sputtered urea schimmelze is compounded with 0.05% by weight of "" Piafol (melamine-formaldehyde condensation product) and 0.2% by weight polyvinyl alcohol.

The prill thinning shows a favorable interlocking of the crystals, static Prillfestigkeit: 1.175 kp

Shatter test residue: 79 #.

Urea melt is admixed with 0.05% by weight of fix-S powder (condensate product of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) and an aqueous concentrated aluminum sulfate solution at 60 ^° C., the aluminum content being based on the Amount of urea, between 0.1 to 0.2 Gewe- $ is set »The 'melt is verprillt

 Static Prick Strength: 1.05 kp Shatter Test Residue: 83 ^.

Example 8

* A urine melt is 0.05 gene. - & Piafol (melamine-formaldehyde condensation product), 0.2 wt .- ^ polyvinyl alcohol and 0.1 Gew $ -> powdered magnesium hydroxide distributed and then sprayed

Static Prill Resistance: 1.22 kp Shatter Test Residue: 91 %.

Example 9

A 70 to 75 #igen urea solution at 80 ⁰ C 0.05

V / ofafix-S powder (Kondensatiönsprodukt of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) and 0.1 wt. S aqueous concentrated aluminum sulfate solution (each based on the urea content in the solution) was added and after homogeneous distribution, the solution to dryness concentrated in vacuo,

- ^r / -

_ "7 _ did

The remaining crystals are melted and sprayed. Static Prick Strength: 0.98 kp Shatter Test Residue: 82 <$>.

Example 10

Wofafix-S powder (condensation product of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) and 0.1% strength by weight aqueous concentrated magnesium sulfate solution before evaporation are obtained analogously to Example 9, the 70% to 75% urea solution 0.05 μg) Static Prick Strength: 1.14 kp Shatter Test Residue: 89 #.

Example 11

Earnstoffschmelze is mixed with a mixture of O, 05 Gevn ~ $ Wofafix-S powder (condensation product of dicyandiamide, formaldehyde, ammonia and ammonium sulfate) and 0.1 wt .- ^ Metakaolin and then sprayed. Static Prill Strength: 1.16 kp Shatter Test ~ Backstage: 91 ^.

Example 12

Analogously to Example 11, a mixture of 0.1% by weight of piafol (melamine / formaldehyde condensation product), 0.1% by weight of polyvinyl alcohol and 0.1% by weight of red mud is added to the urea melt prior to titration.

Static Prill Strength: 1.19 kp

Shade test residue: 90 ^.

Claims (2)

_ 8th - ' *
E rfi η. iu η gsa η s ρ r ü che 1. A process for the preparation of granulated, storable, and free-flowing urea with improved structural and stability properties of the individual prills, characterized in that the urea solution before evaporation or Harnst of fs ciijnelze before spraying condensation products of dicyandiamide, formaldehyde, ammonia and ammonium sulfate and or melamine-formaldehyde condensation products as cation-active polymer electrolytes in a urea-related additional amount of between 0.01 to 0.6% by weight, preferably 0.1 to 0 _s 2% by weight, alone or in gemisoh with magnesium , Aluminum hydroxide, iron hydroxide, wherein the hydroxides can also be produced by addition of magnesium, aluminum or iron salt as a result of reaction with the free ammonia in the solution or melt, dried red mud, metakaoliu, polyvinyl alcohol and / or technical fatty amine mixtures , in amounts of from 0.01 to 0.2 wt .- #, based on the urea, are used. 2. Method according to point 1., characterized in that binary mixtures consisting of 0 _y 01 to 0.2 wt .- ^ of a cationic polymer electrolyte according to item 1 and 0.01 to 0.2 wt S magnesium, aluminum, Eisenhyäroxid, or magnesium, Aluminum or iron salt, red mud, metakaolin, polyvinyl alcohol or technical Fettamingemische be added. 3 · Procedure according to point 1 «, · characterized in that ternary mixtures consisting of 0.01 to 0.2 wt .- ^ of a cationic polymer electrolyte according to item 1, 0.01 to 0.2 polyvinyl alcohol or Metakaiin and 0.01 to 0.2 wt. - 9 - Magnesium, aluminum or iron hydroxide "or magnesium, aluminum or iron salt or red mud or technical Fettamingemisehe be used.