CA1157288A - Process for the production of urea granules - Google Patents
Process for the production of urea granulesInfo
- Publication number
- CA1157288A CA1157288A CA000377380A CA377380A CA1157288A CA 1157288 A CA1157288 A CA 1157288A CA 000377380 A CA000377380 A CA 000377380A CA 377380 A CA377380 A CA 377380A CA 1157288 A CA1157288 A CA 1157288A
- Authority
- CA
- Canada
- Prior art keywords
- urea
- granules
- solution
- weight
- production
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C9/00—Fertilisers containing urea or urea compounds
- C05C9/005—Post-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/30—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic using agents to prevent the granules sticking together; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B19/00—Granulation or pelletisation of phosphatic fertilisers, other than slag
- C05B19/02—Granulation or pelletisation of phosphatic fertilisers, other than slag of superphosphates or mixtures containing them
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
Abstract
Title: A process for the production of urea granules.
Abstract of the disclosure:
The production of urea granules by prilling or granulating a urea melt or an aqueous urea solution, which melt or solution contains a magnesium oxide containing additive. The urea granules thus obtained exhibit a high crushing strength, a high apparent density, and a very low caking tendency, and are suitable for bulk blending with single and triple superphosphate granules.
Abstract of the disclosure:
The production of urea granules by prilling or granulating a urea melt or an aqueous urea solution, which melt or solution contains a magnesium oxide containing additive. The urea granules thus obtained exhibit a high crushing strength, a high apparent density, and a very low caking tendency, and are suitable for bulk blending with single and triple superphosphate granules.
Description
~ 157~f~
For ~he production of urea granules~.various methods are known. One of these is prilling, by which in this speciication is understood a method in which a substantially anhydrous urea melt (havlng a water content of no more than 0.1 to 0.3 % by weight~ is sprayed in the top of a prilling column in a rising stream of air of ambient temperature, in which the droplets solidify.
The resulting prills have a maximum diameter o~ not much more than 3 mm, and are mechanically rather wea~.
Urea granules ha~ing larger dimensions and better mechanical propertles can be produced by the granulation o a substantially anhydrous urea melt in a I .~5~?8~
drum ~ranulator, for example, by the spherodizer tech-nique as described in sritish paten-t 89~,773, or in a pan granulator, for example as described in U.S. patent 4,008,064, or by the granulation of an aqueous urea solution in a fluidized bed, fox example as described in copending Canadian patent application serial no. 303~575, filed May 17, 1978, now Canadian patent 1,101,641 issued May 26, 1981. In the process described in the last-mentioned reference, an aqueous urea solution having a urea concentration of 70 - 99.9 % by weight, preferably 85 - 96 ~ by weight, is sprayed in the form of very fine droplets having an avera~e diameter oE 20 - 120 micron into a fluidized bed of urea particles at a temperature at which the water evaporates from the solution sprayed onto the particles, and urea solidifies on the particles to form granules having a desired size which may be 25 mm and more. As, in this process, rather large amounts of flydust are formed, especially if the urea solution used as the starting material contains more than 5% by weight of water, in particular more than 10 by weight o~ water, preferably a crystalliæation re-tarder for the urea, in particular a water-soluble addition or condensation produc-t of formaldehyde and urea, is added to the urea solution, whereby the for-mation of flydust is suppressed practically completely.
The result of the presence of the crystallization re-tarder is that the granules remain plastic as they are being formed, so that owing to rolling and/or impacts during the formation mechanically strong, smooth and round granules may be formed.
~`~
mab/
I ~57~
~ .
The resulting granules have a high crushing strength, a high impact resistance, and little tendency of forming flydust through ahrasion, and moreover do not cake together, not e~en upon prolonged storage, although urea exhibits a strong natural tendency of caking toge~her.
Urea granules produced according to one of the known methods cannot be used for the production of heterogeneous binary and ternary fertilizer mixtures, such as N-P or N-P-K mixtures by bulk blending with the cheap superphosphabeor triple sup~hosFhate~ as such urea granules are incompatible with these phosphates.~ixtures of such urea granules with superphosphate or triple superphosphate granules deliquesce ater some time to orm an unmanageable and unusahle mud. According to a paper ~y G. Hoffimeister and G.H. Megar, presented during "The Fertilizer I~dustr~
Round Table" on November 6, 1975, at Washington D.C., this ~ncompatibllity is caused by a reaction according to the following equation Ca(H2PO~)2-H2O 4 CO(N~2)~ Ca(H2PO4~2~ 4 ~(NH2)2 H2 By the reaction o~ 1 mol monocalcium phosphate monohydrate, the main component of superphosphate and triple superphosphate, with 4 mols urea, a urea monocalcium phosphate adduct is foDmed, with 1 mol water beiny released. As the adduct has a high solubility, it is readily dissolved in the water liberated to ~orm a large volume of solution, which wets the granules in the mixture, owing to which the reaction proceeds at an ever ~aster rate. Up u~til now, no commercially acceptable means have been ~ound ~o make urea i ~572~3 compatible with superphospha-te or tri.pl.e superphosphate.
As a consequence, it is virtually only the more expensive phosphate fertilizers monoammonium phospha-~e and d.iarn-monium phosphate -that can be used for bulk blending with urea.
It is an object of the present invention to provide a process for the production of urea granules having extraordinary properties, including compatibility with superphosphate and triple superphosphate granules.
According to the invention, there is provided a process for the production of urea granules 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 contains a magnesium oxide containing additive.
According to a more particular aspect of the invention there is provided a process for the production of urea granules wherein an aqueous urea solution having a urea concentration of at least 70% by weight and con-taining a crystallization retarder for the urea is sprayed in the form of very fine droplets into a fluidized bed of urea particles at a temperature at which water evapor-ates from the solution sprayed onto the particles and urea solidifies on the particles to form granules having a desired size, characterized by using as the crystal-lization retarder for the urea in the aqueous urea solu-tion MgO as such or in the form of selectively or com-pletely calcined dolomite in an amount of 0.1-2.0% by weight of MgO, calculated on the urea in the solution.
It has surprisingly been found that the gran-ules produced according to the invention are compatible with superphosphate and triple superphosphate granules, mab/~
~ 157~
by virtue oE which they are suitable for bulk blendiny with these phosphate Eer-tilizers. Mixtures of urea gran-ules obtained according to the invention with superphos-phate granules or triple superphosphate granules that were subjected to the "TVA Bottle Test" a-t 27C were still dry after 7 weeks, whereas analogous mixtures with urea granules not produced in accordance with the invention had deliquesced completely after 3 days.
It has further been found that the presence of magnesium oxide during the prilling or granulation of a urea melt or solution has for its result that the build-up 5a -mab/
1 ~72~
of the granules proceeds flawlessly, and the formation of flydust is prevented, while in addition the resulting urea granules have a very high crushing strength and a very high apparent specific gravity. A furthex highly surprising feature is that the urea granules produced accordl~g to the invention do not cake together, not even upon prolonged storage.
. The magnesium oxide can be used as such (MgO) or in the form of fully calcined dolomite (MgO t CaO) or of selecti~ely calclned dolomite (~gO ~ CaCO3). A beneficial effect is alre~dy obser~ed with a quantity of additive corresponding to 0.1% by weight o MgO, calculated on the urea in the melt or solution~
Preferably the additive is used in a quantity corresponding to 0.5 - 2~ by weight of MgO, calculated on the urea in the melt or solution. I desired, higher proportions may ~e used, but this does not offer any particular advantages.
The additive may be added in the form o~ a powder to the urea melt or solution prior to prilling or granulating.
Preferably, after their formation the granules are cooled to 30C or to a lower temperature, for example by means of a stream of a1r, the moisture content of which has preferably been reduced to such an extent that during the cooling process the granules do not absorb moisture from the cool air.
The invention also relates to compat~ble, heterogeneous fertilizer mixtures of urea granules obtained by the process acc~rding to the present invention with I 1 5 7~
superphosphate or triple superphosphate granules, and, if desired, one or more other granul~ substances.
In addi-tion to urea and superphosphate or triple superphosphate, a potassium f~lizer is mcstly inclu~ed in the mixture, such as KCl. To prevent segregation of the mixture, the granule dLmensions of the components to be blended must be adapted to one another.
For further information regarding the production of fertilizer granules, reference is made with regard to prilling to U.S. patent 3,130,225, with regard to granulation in a pan granulator to U.S. patent 4,008,064, with regard to granulation in a drum granulator to British patent 894,773 and with regard to granulation ln a fluidized bed to copending application 303~575.
The effect of the process according to the invention is shown in and by the following examples.
The "TVA Bottle Test" referred to in the examples serves to determine the compatibility of urea granules with superphosphate and triple superphosphate granules. In this test, a mixture of the urea granules to be tested with superphosphate or triple superphosphate granules was kept in a closed bottle of 12Q cm3 at 27C, and the condition was periodically inspected. The condition observed is evaluated as follows:
. ., ~ ~.572 Condition ~.r ~
D ~ dry, free-flowing W-l = moisture patches, but usable W-2 = moist and slightly sticky, bu-t probably usable W-3 = wet through and sticky, unsuitable for use ~-4 = very wet, unsuitable for use H = hard caked together, unsuitable for use.
In the "bag test" referred to in the examples, the caking tendency of the granules tested was determined.
In this test urea granules were packed in bags of 35 kg, which were stored under a weight of 100~ kg at 27Co After 1 month, the average number of lumps per bag was determined, and the average hardness of the lumps was measured. By hardness is understood here the force in kg, exercised by a dynamometer to cause a lump o~ 7 x 7 x 5 cm to disintegrate.
The crystalli~ation retarder F 80, referred to in the examples, is a clear viscous liquid commercially available under the trade mark of Formurea 80, which is stable between -20C and +40C, and upon analysis is found to contain per 100 parts by weight approximately 20 parts by weight of water, approximately 23 parts by weight of urea and approximately 57 parts by weight of formaldehyde, approximately 55% of the formaldehyde being bound as trimethyl urea, and the balance being present in the unbound state.
1 1~72~
Example .
Tes~ were conducted in whi~h an aqueous urea solution with ancl without a known crystallization retarder (F 80) and with magnesium oxide as a crystallization retarder was sprayed into a fluidized bed of urea particles.
The granulation conditions and the physical properties of the resulting granules are listed in Tabel P,.
Table A
Crystallization retarder none 196 F80 0.6 MgO 1% MgO
Granulation conditions urea solution - concentration,~l~ w~Lght. ~1~.6 94.5 94.5 94.5 -- temperature, C 130 130 130 130 - rate of flow, kg~h 280 280 280 280 injection air - rate of flow, Nm3/h 130 130 130 130 - temperature, C 140 140 140 140 fluidization air - rate of flow, Nm3/h 850 850 850 850 - temperature, C 45 64 54 58 bed temperature, C 108 105 104 104 Product properties - apparent density, g/cm3 1O23 1.26 1.30 1.31 - crushing strengh dia~2.5 mm, kg 2.1 2.8 4.0 4.3 - fly- dust, g/kg 5.4 Co.l 0.1 C 0.1 1 ~572~
Table A (continued) (crystallization retarder none 1% F80 0.6 MgO 1% MgO) Product properties (c~ntinued) - bag test - lumps, % 100 10 0 0 - hardness, kg 22 0.1 0 0 - TVA Bottle Test ..
with superph~sphate-~SSP) 50/50 ater 1 day W-2 W~2 D D
after 3 days W-4 W-4 D D
after 7 days W-4 W-4 D D
after 14 days W-4 W-4 W-l D
after 21 days W-4 W-4 W-1 D
after 50 days W-4 W-4 W-l D
wi~h triple superphosphate (TSP) 50/50 a~ter 1 day W-~ W-2 D D
after 3 days W-4 W-4 D D
aft~r 7 days W-4 W-4 D D
after 14 days W-4 W-4 W-1 D
after 21 days W-4 W-4 W-l D
after 50 days W 4 W-4 W-l D
A subsequent series o~ tests were conducted analogously to those described in Example I, but usin~
selectively calcined dolomite and completely calcined dolomite as crystallization retarders instead of magnesium oxide. The granulation conditions and the p~ysical properties of the resulting granules are listed in ~able B.
1 ~572~
CD
d~
C~
_I ~ o o c~ ~ o r ~ ~ ~ ~ ~ ~ ~ U~
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U~ o o o o o ~ Lr~
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E~ O ~r o o o o o ~ o ~ ~ o ~ ~ U~ U~ o 'b _, a~
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a) .,1 dP U ,X ~ O ~ U
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~ o ~
~ ~ ~ ~ o ~ ~ ~
N O ~ ~ J ~ ~ rl ~\ ~1 ~1 ~
O O O ~ ~ O S~
~1 1~ o ~ N a) E~i .
u~ ~ ~ O i~
:~ ~ a~ u ~ ~ . n 5 ~ U ~
-12- 1 15~2~
rd ~ ~ ~ ~
dP ~
a Q
~1 ~ ~ o ~ N h 0 h ~d 1~ ~ N O o Ui O O U~
U
O
~-1 a~ ~
F3 _~ ~ o o N h O~ O O IJ~ O O Ul U~ U~
o~
~~ . . , ra~
_I --~ ~ O r~
U ~
O
~ ~ ~ c~
rl U~p N o alUl ' ~ ~Q
~:--I ~~1 ~ o a~
0 ~1 u tn -U
~: o q~ Ql ~ a ~n C) _l ,, Q) `
~a a~ ~ ~ ~
~ ~ ~ n o o O ~
J ~ ~ ~ O O
1~1 Q ~ ' N O ~ U~
Q ~ 0 _l ~ O cn E~
~ s~ m ~t ~ ~ h ~
O 1~ 3 ~ l l l l l Example III
A substantially anhydrous urea melt with and without added magnesium oxide was sprayed in the top of a prilling column in a rising stream of air o~ ambient temperature. The physical properties of the xesulting prilLs are listed in Table C.
Table C
Additive none 0.72~ MgO 0.95% MgO
Product pro~ties - apparent density, g/Gm3 1.30 1.32 1.33 - crushing strength, dia. 2.5 mm, kg 0.54 1.04 1.16 - bag test - ltL~pS, ~ 100 0 . O
- hardness, kg. 9 0 0 - T~A Bottle Test with SSP 50/50 after 3 days more than more than deliquesced 60 days 60 days usable usable with TSP 50/50 after 3 days more than more than del~quesced 60 days 60 days usable usable Example IV
A urea melt to which magnesium oxide had been added was granulated in a rotary horizontal granulation drum having a diameter of 90 cm and a width of 60 cm. The arum was provided on its inner wall with eight longitwdinal strips of 3.5 x 60 ~m spaced equal distances from each other. The speed was 15 rpm. The drum was filled with 1 1S7;~8 60 kg ur~a granules having an average diameter of 1.8 mm and a temperature of 80C. Using two hydraulic sprayers, 60 kg anhydrous urea melt (99.8% by weight of urea), to which O.6 ~ by weight of MgO had been added, having a temperature o~ 140-145C was sprayed into the rotary drum at a rate of approximately 100 kg/h over the granules showered from the longitudinal strips. The granulation was effected at At the Pnd of the test, the granules were cooled to approæimately 30C and sieved. The product granules had a good roundness and a smooth surface. Their apparent density was 1.288 g/cm3 and the crushing strength dia. 2.5 mm was 3.5 kg. Flydust formation was 3.g g/kg. The granules had ~irtually no caking tendency. 50/50 blends with SSP
and with TSP were usable for more than 60 days. The sieve analysis of the product was as follows:
> 4.00 mm : 17%
4.00-2.5 mm : 46%
For ~he production of urea granules~.various methods are known. One of these is prilling, by which in this speciication is understood a method in which a substantially anhydrous urea melt (havlng a water content of no more than 0.1 to 0.3 % by weight~ is sprayed in the top of a prilling column in a rising stream of air of ambient temperature, in which the droplets solidify.
The resulting prills have a maximum diameter o~ not much more than 3 mm, and are mechanically rather wea~.
Urea granules ha~ing larger dimensions and better mechanical propertles can be produced by the granulation o a substantially anhydrous urea melt in a I .~5~?8~
drum ~ranulator, for example, by the spherodizer tech-nique as described in sritish paten-t 89~,773, or in a pan granulator, for example as described in U.S. patent 4,008,064, or by the granulation of an aqueous urea solution in a fluidized bed, fox example as described in copending Canadian patent application serial no. 303~575, filed May 17, 1978, now Canadian patent 1,101,641 issued May 26, 1981. In the process described in the last-mentioned reference, an aqueous urea solution having a urea concentration of 70 - 99.9 % by weight, preferably 85 - 96 ~ by weight, is sprayed in the form of very fine droplets having an avera~e diameter oE 20 - 120 micron into a fluidized bed of urea particles at a temperature at which the water evaporates from the solution sprayed onto the particles, and urea solidifies on the particles to form granules having a desired size which may be 25 mm and more. As, in this process, rather large amounts of flydust are formed, especially if the urea solution used as the starting material contains more than 5% by weight of water, in particular more than 10 by weight o~ water, preferably a crystalliæation re-tarder for the urea, in particular a water-soluble addition or condensation produc-t of formaldehyde and urea, is added to the urea solution, whereby the for-mation of flydust is suppressed practically completely.
The result of the presence of the crystallization re-tarder is that the granules remain plastic as they are being formed, so that owing to rolling and/or impacts during the formation mechanically strong, smooth and round granules may be formed.
~`~
mab/
I ~57~
~ .
The resulting granules have a high crushing strength, a high impact resistance, and little tendency of forming flydust through ahrasion, and moreover do not cake together, not e~en upon prolonged storage, although urea exhibits a strong natural tendency of caking toge~her.
Urea granules produced according to one of the known methods cannot be used for the production of heterogeneous binary and ternary fertilizer mixtures, such as N-P or N-P-K mixtures by bulk blending with the cheap superphosphabeor triple sup~hosFhate~ as such urea granules are incompatible with these phosphates.~ixtures of such urea granules with superphosphate or triple superphosphate granules deliquesce ater some time to orm an unmanageable and unusahle mud. According to a paper ~y G. Hoffimeister and G.H. Megar, presented during "The Fertilizer I~dustr~
Round Table" on November 6, 1975, at Washington D.C., this ~ncompatibllity is caused by a reaction according to the following equation Ca(H2PO~)2-H2O 4 CO(N~2)~ Ca(H2PO4~2~ 4 ~(NH2)2 H2 By the reaction o~ 1 mol monocalcium phosphate monohydrate, the main component of superphosphate and triple superphosphate, with 4 mols urea, a urea monocalcium phosphate adduct is foDmed, with 1 mol water beiny released. As the adduct has a high solubility, it is readily dissolved in the water liberated to ~orm a large volume of solution, which wets the granules in the mixture, owing to which the reaction proceeds at an ever ~aster rate. Up u~til now, no commercially acceptable means have been ~ound ~o make urea i ~572~3 compatible with superphospha-te or tri.pl.e superphosphate.
As a consequence, it is virtually only the more expensive phosphate fertilizers monoammonium phospha-~e and d.iarn-monium phosphate -that can be used for bulk blending with urea.
It is an object of the present invention to provide a process for the production of urea granules having extraordinary properties, including compatibility with superphosphate and triple superphosphate granules.
According to the invention, there is provided a process for the production of urea granules 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 contains a magnesium oxide containing additive.
According to a more particular aspect of the invention there is provided a process for the production of urea granules wherein an aqueous urea solution having a urea concentration of at least 70% by weight and con-taining a crystallization retarder for the urea is sprayed in the form of very fine droplets into a fluidized bed of urea particles at a temperature at which water evapor-ates from the solution sprayed onto the particles and urea solidifies on the particles to form granules having a desired size, characterized by using as the crystal-lization retarder for the urea in the aqueous urea solu-tion MgO as such or in the form of selectively or com-pletely calcined dolomite in an amount of 0.1-2.0% by weight of MgO, calculated on the urea in the solution.
It has surprisingly been found that the gran-ules produced according to the invention are compatible with superphosphate and triple superphosphate granules, mab/~
~ 157~
by virtue oE which they are suitable for bulk blendiny with these phosphate Eer-tilizers. Mixtures of urea gran-ules obtained according to the invention with superphos-phate granules or triple superphosphate granules that were subjected to the "TVA Bottle Test" a-t 27C were still dry after 7 weeks, whereas analogous mixtures with urea granules not produced in accordance with the invention had deliquesced completely after 3 days.
It has further been found that the presence of magnesium oxide during the prilling or granulation of a urea melt or solution has for its result that the build-up 5a -mab/
1 ~72~
of the granules proceeds flawlessly, and the formation of flydust is prevented, while in addition the resulting urea granules have a very high crushing strength and a very high apparent specific gravity. A furthex highly surprising feature is that the urea granules produced accordl~g to the invention do not cake together, not even upon prolonged storage.
. The magnesium oxide can be used as such (MgO) or in the form of fully calcined dolomite (MgO t CaO) or of selecti~ely calclned dolomite (~gO ~ CaCO3). A beneficial effect is alre~dy obser~ed with a quantity of additive corresponding to 0.1% by weight o MgO, calculated on the urea in the melt or solution~
Preferably the additive is used in a quantity corresponding to 0.5 - 2~ by weight of MgO, calculated on the urea in the melt or solution. I desired, higher proportions may ~e used, but this does not offer any particular advantages.
The additive may be added in the form o~ a powder to the urea melt or solution prior to prilling or granulating.
Preferably, after their formation the granules are cooled to 30C or to a lower temperature, for example by means of a stream of a1r, the moisture content of which has preferably been reduced to such an extent that during the cooling process the granules do not absorb moisture from the cool air.
The invention also relates to compat~ble, heterogeneous fertilizer mixtures of urea granules obtained by the process acc~rding to the present invention with I 1 5 7~
superphosphate or triple superphosphate granules, and, if desired, one or more other granul~ substances.
In addi-tion to urea and superphosphate or triple superphosphate, a potassium f~lizer is mcstly inclu~ed in the mixture, such as KCl. To prevent segregation of the mixture, the granule dLmensions of the components to be blended must be adapted to one another.
For further information regarding the production of fertilizer granules, reference is made with regard to prilling to U.S. patent 3,130,225, with regard to granulation in a pan granulator to U.S. patent 4,008,064, with regard to granulation in a drum granulator to British patent 894,773 and with regard to granulation ln a fluidized bed to copending application 303~575.
The effect of the process according to the invention is shown in and by the following examples.
The "TVA Bottle Test" referred to in the examples serves to determine the compatibility of urea granules with superphosphate and triple superphosphate granules. In this test, a mixture of the urea granules to be tested with superphosphate or triple superphosphate granules was kept in a closed bottle of 12Q cm3 at 27C, and the condition was periodically inspected. The condition observed is evaluated as follows:
. ., ~ ~.572 Condition ~.r ~
D ~ dry, free-flowing W-l = moisture patches, but usable W-2 = moist and slightly sticky, bu-t probably usable W-3 = wet through and sticky, unsuitable for use ~-4 = very wet, unsuitable for use H = hard caked together, unsuitable for use.
In the "bag test" referred to in the examples, the caking tendency of the granules tested was determined.
In this test urea granules were packed in bags of 35 kg, which were stored under a weight of 100~ kg at 27Co After 1 month, the average number of lumps per bag was determined, and the average hardness of the lumps was measured. By hardness is understood here the force in kg, exercised by a dynamometer to cause a lump o~ 7 x 7 x 5 cm to disintegrate.
The crystalli~ation retarder F 80, referred to in the examples, is a clear viscous liquid commercially available under the trade mark of Formurea 80, which is stable between -20C and +40C, and upon analysis is found to contain per 100 parts by weight approximately 20 parts by weight of water, approximately 23 parts by weight of urea and approximately 57 parts by weight of formaldehyde, approximately 55% of the formaldehyde being bound as trimethyl urea, and the balance being present in the unbound state.
1 1~72~
Example .
Tes~ were conducted in whi~h an aqueous urea solution with ancl without a known crystallization retarder (F 80) and with magnesium oxide as a crystallization retarder was sprayed into a fluidized bed of urea particles.
The granulation conditions and the physical properties of the resulting granules are listed in Tabel P,.
Table A
Crystallization retarder none 196 F80 0.6 MgO 1% MgO
Granulation conditions urea solution - concentration,~l~ w~Lght. ~1~.6 94.5 94.5 94.5 -- temperature, C 130 130 130 130 - rate of flow, kg~h 280 280 280 280 injection air - rate of flow, Nm3/h 130 130 130 130 - temperature, C 140 140 140 140 fluidization air - rate of flow, Nm3/h 850 850 850 850 - temperature, C 45 64 54 58 bed temperature, C 108 105 104 104 Product properties - apparent density, g/cm3 1O23 1.26 1.30 1.31 - crushing strengh dia~2.5 mm, kg 2.1 2.8 4.0 4.3 - fly- dust, g/kg 5.4 Co.l 0.1 C 0.1 1 ~572~
Table A (continued) (crystallization retarder none 1% F80 0.6 MgO 1% MgO) Product properties (c~ntinued) - bag test - lumps, % 100 10 0 0 - hardness, kg 22 0.1 0 0 - TVA Bottle Test ..
with superph~sphate-~SSP) 50/50 ater 1 day W-2 W~2 D D
after 3 days W-4 W-4 D D
after 7 days W-4 W-4 D D
after 14 days W-4 W-4 W-l D
after 21 days W-4 W-4 W-1 D
after 50 days W-4 W-4 W-l D
wi~h triple superphosphate (TSP) 50/50 a~ter 1 day W-~ W-2 D D
after 3 days W-4 W-4 D D
aft~r 7 days W-4 W-4 D D
after 14 days W-4 W-4 W-1 D
after 21 days W-4 W-4 W-l D
after 50 days W 4 W-4 W-l D
A subsequent series o~ tests were conducted analogously to those described in Example I, but usin~
selectively calcined dolomite and completely calcined dolomite as crystallization retarders instead of magnesium oxide. The granulation conditions and the p~ysical properties of the resulting granules are listed in ~able B.
1 ~572~
CD
d~
C~
_I ~ o o c~ ~ o r ~ ~ ~ ~ ~ ~ ~ U~
~ o ,, o dP In U~
U~ o o o o o ~ Lr~
O
t~ _I~ ~ ~1 OD
d~ U~
t~
,, Ln o o o o~ o U ~
~_I
_, ~
a~ o _I
o C) Q~
. u~ o c~ o ~r o ~Q
a~
~ ~ ~ .
E~ O ~r o o o o o ~ o ~ ~ o ~ ~ U~ U~ o 'b _, a~
~a o .4 .~
a) .,1 dP U ,X ~ O ~ U
~ ~ o o ~ o o ou o 0 ~ s~, o ~
~ o ~
~ ~ ~ ~ o ~ ~ ~
N O ~ ~ J ~ ~ rl ~\ ~1 ~1 ~
O O O ~ ~ O S~
~1 1~ o ~ N a) E~i .
u~ ~ ~ O i~
:~ ~ a~ u ~ ~ . n 5 ~ U ~
-12- 1 15~2~
rd ~ ~ ~ ~
dP ~
a Q
~1 ~ ~ o ~ N h 0 h ~d 1~ ~ N O o Ui O O U~
U
O
~-1 a~ ~
F3 _~ ~ o o N h O~ O O IJ~ O O Ul U~ U~
o~
~~ . . , ra~
_I --~ ~ O r~
U ~
O
~ ~ ~ c~
rl U~p N o alUl ' ~ ~Q
~:--I ~~1 ~ o a~
0 ~1 u tn -U
~: o q~ Ql ~ a ~n C) _l ,, Q) `
~a a~ ~ ~ ~
~ ~ ~ n o o O ~
J ~ ~ ~ O O
1~1 Q ~ ' N O ~ U~
Q ~ 0 _l ~ O cn E~
~ s~ m ~t ~ ~ h ~
O 1~ 3 ~ l l l l l Example III
A substantially anhydrous urea melt with and without added magnesium oxide was sprayed in the top of a prilling column in a rising stream of air o~ ambient temperature. The physical properties of the xesulting prilLs are listed in Table C.
Table C
Additive none 0.72~ MgO 0.95% MgO
Product pro~ties - apparent density, g/Gm3 1.30 1.32 1.33 - crushing strength, dia. 2.5 mm, kg 0.54 1.04 1.16 - bag test - ltL~pS, ~ 100 0 . O
- hardness, kg. 9 0 0 - T~A Bottle Test with SSP 50/50 after 3 days more than more than deliquesced 60 days 60 days usable usable with TSP 50/50 after 3 days more than more than del~quesced 60 days 60 days usable usable Example IV
A urea melt to which magnesium oxide had been added was granulated in a rotary horizontal granulation drum having a diameter of 90 cm and a width of 60 cm. The arum was provided on its inner wall with eight longitwdinal strips of 3.5 x 60 ~m spaced equal distances from each other. The speed was 15 rpm. The drum was filled with 1 1S7;~8 60 kg ur~a granules having an average diameter of 1.8 mm and a temperature of 80C. Using two hydraulic sprayers, 60 kg anhydrous urea melt (99.8% by weight of urea), to which O.6 ~ by weight of MgO had been added, having a temperature o~ 140-145C was sprayed into the rotary drum at a rate of approximately 100 kg/h over the granules showered from the longitudinal strips. The granulation was effected at At the Pnd of the test, the granules were cooled to approæimately 30C and sieved. The product granules had a good roundness and a smooth surface. Their apparent density was 1.288 g/cm3 and the crushing strength dia. 2.5 mm was 3.5 kg. Flydust formation was 3.g g/kg. The granules had ~irtually no caking tendency. 50/50 blends with SSP
and with TSP were usable for more than 60 days. The sieve analysis of the product was as follows:
> 4.00 mm : 17%
4.00-2.5 mm : 46%
2.5 - 2.0 mm : 29%
< 2.0 mm o 8%
average diameter : 3.0 mm.
< 2.0 mm o 8%
average diameter : 3.0 mm.
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the production of urea granules wherein an aqueous urea solution having a urea concen-tration of at least 70% by weight and containing a crys-tallization retarder for the urea is sprayed in the form of very fine droplets into a fluidized bed of urea par-ticles at a temperature at which water evaporates from the solution sprayed onto the particles and urea soli-difies on the particles to form granules having a de-sired size, characterized by using as the crystallization retarder for the urea in the aqueous urea solution MgO as such or in the form of selectively or completely calcined dolomite in an amount of 0.1-2.0 % by weight of MgO, calculated on the urea in the solution.
2. A process as claimed in claim 1, wherein the aqueous urea solution has a urea concentration of 85-96 % by weight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8002912 | 1980-05-20 | ||
| NL8002912A NL8002912A (en) | 1980-05-20 | 1980-05-20 | METHOD FOR MAKING UREA GRANULES, AND ARTICLES OF FERTILIZER MIXTURES INCLUDED THEREFORE. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157288A true CA1157288A (en) | 1983-11-22 |
Family
ID=19835332
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000377380A Expired CA1157288A (en) | 1980-05-20 | 1981-05-12 | Process for the production of urea granules |
Country Status (28)
| Country | Link |
|---|---|
| JP (1) | JPS6035320B2 (en) |
| AT (1) | AT375917B (en) |
| BE (1) | BE888842A (en) |
| BG (1) | BG49613A3 (en) |
| BR (1) | BR8103139A (en) |
| CA (1) | CA1157288A (en) |
| CS (1) | CS259506B2 (en) |
| DD (1) | DD159040A5 (en) |
| DE (1) | DE3118454C2 (en) |
| EG (1) | EG15440A (en) |
| ES (1) | ES502903A0 (en) |
| FI (1) | FI71721C (en) |
| FR (1) | FR2482871B1 (en) |
| GB (1) | GB2077722B (en) |
| GR (1) | GR75604B (en) |
| HU (1) | HU184438B (en) |
| IE (1) | IE51964B1 (en) |
| IN (1) | IN153960B (en) |
| IT (1) | IT1136617B (en) |
| MX (1) | MX160067A (en) |
| NL (2) | NL8002912A (en) |
| NO (1) | NO151648C (en) |
| PL (1) | PL134458B1 (en) |
| PT (1) | PT73053B (en) |
| SE (1) | SE446625B (en) |
| TR (1) | TR21674A (en) |
| YU (1) | YU42568B (en) |
| ZA (1) | ZA813280B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4943308A (en) * | 1985-10-17 | 1990-07-24 | Hydro Agri Sluiskil B.V. | Method of producing fertilizer granules containing urea and ammonium sulphate |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3117542A1 (en) * | 1981-05-04 | 1983-02-10 | Franz Josef Gattys Ingenieurbüro für Chem. Maschinen- und Apparatebau, 6078 Neu-Isenburg | METHOD FOR STABILIZING DEHYDRATED MAGNESIUM CHLORIDE AGAINST RUECK HYDRATION |
| GR76402B (en) * | 1981-07-03 | 1984-08-10 | Azote Sa Cie Neerlandaise | |
| DE4232567C1 (en) * | 1992-09-29 | 1994-02-10 | Kali & Salz Ag | Granular sulphate fertiliser treatment to prevent dust formation during bulk transformation - comprises spraying with conc. urea soln. |
| AUPM383594A0 (en) * | 1994-02-11 | 1994-03-10 | Incitec Ltd | Granular urea |
| AU679330B2 (en) * | 1994-02-11 | 1997-06-26 | Incitec Ltd | Granular urea |
| DE102005018949A1 (en) * | 2005-04-18 | 2006-10-19 | Ami-Agrolinz Melamine International Gmbh | Solid particles production, especially urea particles, from flowable starting material containing e.g. actinium oxide, useful e.g. in catalysts or milling bodies, comprises splitting into droplets and introducing into solidification liquid |
| DE102021108187A1 (en) | 2021-03-31 | 2022-10-06 | Skw Stickstoffwerke Piesteritz Gmbh | Granulated pH neutral urea ammonium sulphate fertilizer with urease inhibitor |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB731686A (en) * | 1952-06-25 | 1955-06-15 | Ici Ltd | Improvements in and relating to urea compositions |
| GB837163A (en) * | 1958-01-31 | 1960-06-09 | Ici Ltd | Improvements in and relating to urea compositions |
| GB1220826A (en) * | 1967-09-13 | 1971-01-27 | Fisons Ltd | Process for the production of particulate urea |
-
1980
- 1980-05-20 NL NL8002912A patent/NL8002912A/en not_active Application Discontinuation
-
1981
- 1981-05-04 NL NL8102191A patent/NL8102191A/en not_active Application Discontinuation
- 1981-05-09 DE DE3118454A patent/DE3118454C2/en not_active Expired
- 1981-05-12 CA CA000377380A patent/CA1157288A/en not_active Expired
- 1981-05-12 IE IE1062/81A patent/IE51964B1/en unknown
- 1981-05-12 IN IN501/CAL/81A patent/IN153960B/en unknown
- 1981-05-12 GR GR64915A patent/GR75604B/el unknown
- 1981-05-14 AT AT0215381A patent/AT375917B/en not_active IP Right Cessation
- 1981-05-15 GB GB8115005A patent/GB2077722B/en not_active Expired
- 1981-05-15 FR FR8109729A patent/FR2482871B1/en not_active Expired
- 1981-05-18 ZA ZA00813280A patent/ZA813280B/en unknown
- 1981-05-19 IT IT21817/81A patent/IT1136617B/en active
- 1981-05-19 HU HU811441A patent/HU184438B/en not_active IP Right Cessation
- 1981-05-19 SE SE8103139A patent/SE446625B/en not_active IP Right Cessation
- 1981-05-19 FI FI811539A patent/FI71721C/en not_active IP Right Cessation
- 1981-05-19 BE BE2/59164A patent/BE888842A/en not_active IP Right Cessation
- 1981-05-19 MX MX187383A patent/MX160067A/en unknown
- 1981-05-19 PT PT73053A patent/PT73053B/en not_active IP Right Cessation
- 1981-05-19 YU YU1285/81A patent/YU42568B/en unknown
- 1981-05-19 JP JP56074344A patent/JPS6035320B2/en not_active Expired
- 1981-05-19 NO NO811697A patent/NO151648C/en unknown
- 1981-05-19 CS CS813720A patent/CS259506B2/en unknown
- 1981-05-20 PL PL1981231271A patent/PL134458B1/en unknown
- 1981-05-20 DD DD81230122A patent/DD159040A5/en not_active IP Right Cessation
- 1981-05-20 EG EG283/81A patent/EG15440A/en active
- 1981-05-20 TR TR21674A patent/TR21674A/en unknown
- 1981-05-20 BG BG52155A patent/BG49613A3/en unknown
- 1981-05-20 BR BR8103139A patent/BR8103139A/en not_active IP Right Cessation
- 1981-05-20 ES ES502903A patent/ES502903A0/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4943308A (en) * | 1985-10-17 | 1990-07-24 | Hydro Agri Sluiskil B.V. | Method of producing fertilizer granules containing urea and ammonium sulphate |
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