WO2018096495A1 - Installation et procédé pour la production d'urée solide en granulés - Google Patents

Installation et procédé pour la production d'urée solide en granulés Download PDF

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Publication number
WO2018096495A1
WO2018096495A1 PCT/IB2017/057385 IB2017057385W WO2018096495A1 WO 2018096495 A1 WO2018096495 A1 WO 2018096495A1 IB 2017057385 W IB2017057385 W IB 2017057385W WO 2018096495 A1 WO2018096495 A1 WO 2018096495A1
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Prior art keywords
urea
cooling liquid
tank
production
density
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Ceased
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PCT/IB2017/057385
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English (en)
Inventor
Giacomo Cavuoti
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EUROTECNICA MELAMINE LUXEMBURG ZWEIGNIEDERLASSUNG IN ITTIGEN
Original Assignee
EUROTECNICA MELAMINE LUXEMBURG ZWEIGNIEDERLASSUNG IN ITTIGEN
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Priority to CN201780072402.4A priority Critical patent/CN110267734A/zh
Publication of WO2018096495A1 publication Critical patent/WO2018096495A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
    • B01J2/06—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a liquid medium
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05C—NITROGENOUS FERTILISERS
    • C05C9/00—Fertilisers containing urea or urea compounds
    • C05C9/005—Post-treatment

Definitions

  • the present invention concerns a plant and a process for the production of solid urea in granules.
  • the present invention refers to a plant for the production of solid urea in granules, capable of operating with a lower energy consumption and having reduced dimensions.
  • the urea is obtained from a reaction of ammonia and carbon dioxide, from which a salt is obtained which melts at 135°C and which, in solution, has a clear colourless appearance.
  • the molten urea undergoes a finishing phase in which it is transformed into a format suitable for subsequent use as an end product, for example fertilizer, animal feed or another type of end product.
  • This finishing phase generally entails treating the molten urea by means of appropriate plants for the production of urea granules, generally in the form of prills.
  • a first known urea granule production plant consists of a cylindrical tower, generally made of reinforced concrete, with typical dimensions up to a height of
  • prilling tower 50 metres and a diameter of 20 metres, which is called prilling tower.
  • a perforated frustoconical distribution basket is provided which distributes a shower of liquid urea as it rotates.
  • urea droplets fall, they pass from the liquid state to the solid state by cooling, thereby forming the urea prills.
  • urea prills thus formed are collected at the bottom of the tower and transported on a conveyor belt to the storage warehouses.
  • the Applicant has observed that said plant, in addition to having imposing dimensions, only allows prills with very small diameters to be obtained, generally equal to 1-2.5 mm.
  • prills with much larger diameter, for example equal to or greater than 8 mm, also known as megaprills are highly desirable in order to obtain a gradual release of nitrogen, uniformly distributed over time.
  • the finishing phase can be performed by means of a plant for the production of solid urea in granules known as fluidized bed granulator which comprises a tank with air blown in from below at a temperature of approx. 40-60 °C.
  • fluidized bed granulator which comprises a tank with air blown in from below at a temperature of approx. 40-60 °C.
  • liquid urea is sprayed from below which, once solidified into small particles, is kept suspended by the air blown in. Continuing to spray liquid urea from below, the particles swell while they are moved by the air, as the liquid urea adheres to their surface and, solidifying, causes them to increase in diameter.
  • the Applicant has found that said plant, like the prilling towers, has imposing dimensions. Furthermore, in order to obtain prills with large diameters, the solidified particles have to be kept in suspension for a long time. This results in an enormous consumption of energy.
  • the nozzles By adopting a low-boiling liquid maintained at a temperature well below the starting temperature of the drops, the nozzles must be kept sufficiently distant from the liquid to prevent the early solidification of the melt, but close enough to prevent crushing of the drop in the collision with the free surface of the cooling bath.
  • the formation of droplets in the gaseous intersection entails an upper limit to their size determined by the balance between surface tension at the nozzle mouth and drop weight less floating force.
  • the drop, as it is generated in this gaseous layer has a very small floating force due to the low density of the gas, and therefore cannot grow beyond a certain size (4-5 mm as stated in the above cited documents).
  • the cooling of the prills is therefore, in all cases, for the first part of the bath, obtained by evaporation of the bath liquid and formation of a vapor film around the drop that prevents it from contact with the liquid.
  • the cooling mechanism for evaporation is the predominant one, taking into account the great difference between the melting temperature of the urea drop (which tends to remain constant even if the cooling occurs by concentric layers of the prill) and the bath temperature (equal to or less than the boiling point of the cooling liquid).
  • lenticular or toroidal shapes could be interesting, for example due to the different surface- volume ratio offered by these shapes.
  • the Applicant has therefore highlighted the need to provide a plant for the production of solid urea in granules which has reduced dimensions and is able to operate with lower energy consumption than the known plants.
  • the Applicant has also recognized the need to provide a plant for the production of solid urea in granules, which is able to produce, in addition to the granule shapes and sizes so far obtainable, urea granules with larger dimensions and different shapes.
  • the problem underlying the present invention is therefore that of producing a plant for the production of solid urea in granules which has compact dimensions and is characterized by reduced energy consumption.
  • one object of the present invention is to conceive a plant for the production of solid urea in granules which is able to obtain urea granules with both diameters larger and smaller than 8 mm.
  • a further object of the present invention is to conceive a plant for the production of solid urea in granules which further allows granules with controlled dimensions and both a spherical and non-spherical shape to be obtained.
  • the invention therefore concerns a plant for the production of solid urea in granules comprising at least one first tank for the formation of urea granules and a dripping unit provided with at least one hole for feeding molten urea in the form of drops into the first tank, characterized in that the first tank is filled with at least one cooling liquid immiscible with molten urea, wherein at least one molten urea feeding hole of the dripping unit is immersed in at least one cooling liquid.
  • cooling liquid means a liquid kept at a temperature below the melting temperature of the urea and in particular at a temperature that facilitates the solidification of the molten urea.
  • the layer of the at least one cooling liquid in which the at least one molten urea feeding hole of the dripping unit is immersed is maintained at a temperature comprised between 110 and 125°C, preferably of from 110 to 120°C, namely at a temperature slightly lower than that of solidification of urea which is equal to 132°C.
  • the energy necessary to maintain the cooling liquid at a sufficiently low temperature to obtain the solidification of the drops of urea is a minimum percentage with respect to the consumption of the known plants.
  • the Applicant has in fact ascertained that, depending on the immiscible liquid used, it is possible to obtain solidification also when the drop travels through the liquid for less than half a metre, i.e. one hundred times shorter than the distance of that required by the prilling towers.
  • the large floating force due to the high density of liquid surrounding the droplet allows to form even larger drops, up to 15 mm or more, which, by solidifying, can produce the so-called megaprills or megagranules (namely with a size of more than 8-9 mm), used as fertilizer in very important agronomic fields such as rice cultivation.
  • Performing solidification in a liquid with an appropriate density also allows urea granule shapes to be obtained, different from the spherical shape, for example lenticular or toroidal.
  • any organic or inorganic compound can be used with a density below the density of the molten urea, in which the urea is insoluble, and the residue of which left on the solidified urea granules, is compatible in terms of quantity and quality with use of the product.
  • the invention concerns a process for the production of solid urea in granules which is characterized by the fact that it comprises the phases consisting in dripping molten urea into a cooling liquid immiscible with molten urea.
  • the process for the production of solid urea in granules according to the invention achieves the technical effects described above in relation to the plant for the production of solid urea in granules according to the invention.
  • the present invention in at least one of the above-mentioned aspects, can have at least one of the following preferred characteristics; the latter are in particular combinable with one another as required in order to meet the specific application needs.
  • At least one molten urea feeding hole of the dripping unit is immersed in at least one cooling liquid.
  • Immersing the feeding hole in the liquid ensures that the solidification process takes place gradually and uniformly, therefore extending right through up to the centre of the drop.
  • At least one cooling liquid has a density below the density of the molten urea, i.e. lower than approximately 1300 kg/m , and the dripping unit is positioned at the free surface of the cooling liquid.
  • Said configuration advantageously allows the solidification of the urea drops in downflow conditions.
  • downstream configuration we mean a configuration in which the urea drops are fed from above and solidify as they fall downwards.
  • the molten urea feeding hole of the dripping unit is immersed into the cooling liquid and, in the downflow configuration, the liquid layer in which the feeding hole is dipped is preferably kept at a temperature ranging of from 110 to 120°C.
  • the lower density of the cooling liquid with respect to the density of the molten urea determines a descent by gravity once delivered into the liquid.
  • At least one cooling liquid with a density lower than the density of the molten urea is chosen from the group consisting of:
  • the edible vegetable oils can be seed oils such as sunflower seed, soybean oil, palm oil, castor oil, olive oil, rapeseed oil and so on.
  • mineral oils can be, for example, Vaseline oil.
  • molten waxes With reference to molten waxes, they preferably have a melting temperature lower than 80°C.
  • Said cooling liquids have a boiling temperature far above the maximum temperature of molten drops of urea (132-140°C) and therefore cooling is carried out without evaporation, with liquid-liquid direct contact between the molten urea drop and the bath cooling liquid, with a convective thermal exchange due to the relative drop speed of urea droplet/prill compared to the quiescent oil bath. Cooling is carried out in-situ, with suitably arranged heat exchange surfaces immersed in the tank, without need of extracting an oil stream, cooling it in an external exchanger and pumping it back into the tank.
  • Cooling is then carried out in liquid phase using non-toxic substances (some substances are also used in the food industry) and without the production and condensation of vapors of potentially dangerous, toxic or flammable substances (such as toluene, cyclohexane, chlorobenzene, carbon tetrachloride, hexane).
  • non-toxic substances such as toluene, cyclohexane, chlorobenzene, carbon tetrachloride, hexane.
  • a coating of the formed granules is automatically obtained which prevents caking, i.e. fusion between individual granules as a result of heat and humidity.
  • At least one polymer resin is added to at least one cooling liquid.
  • said resin adheres to the surface of the granule generated, forming a coating, thus making it unnecessary to purposely coat the granules in order to slow down the rapid drainage from rainwater and regulate the release of urea over time, especially in association with the use of megagranules (granules with diameters equal to or greater than 8-9 mm).
  • heavy powders and/or micropowders are added to at least one cooling liquid.
  • silica, glass microspheres, metal powders, fossil flour and so on can be used as powders and/or micropowders.
  • means for generation of a current of at least one cooling liquid from the bottom to the top are provided.
  • an inclined wall is provided, which extends between a portion positioned at a higher level and a portion positioned at a lower level, a transport unit being arranged at the surface portion at a higher level for conveying urea granules flowing out of at least one first tank.
  • a unit for generation of a current of cooling liquid is preferably provided at the bottom of at least one first tank.
  • the unit for generation of a current of cooling liquid is designed to generate a current directed towards the conveying unit.
  • the inclined wall positioned on the bottom and/or the current of cooling liquid convey the prills deposited on the bottom towards the transport unit, facilitating the outflow from the tank.
  • the transport unit is partially immersed in at least one first granule formation tank and is preferably made like a perforated conveyer belt with scrapers or perforated bucket elevator or screw elevator.
  • At least one blower for the evaporation of the cooling liquid is associated with the transport unit.
  • the cold current of cooling liquid which flows on the bottom is kept separate from the cooling fluid above by means of a plurality of flow separating partitions.
  • a plurality of cooling plates is arranged.
  • At least one first tank is filled in addition with a second cooling liquid immiscible with molten urea and having a density higher than the density of the molten urea, a connection opening being provided at the bottom of at least one first tank to a second tank, the second tank being filled with the second cooling liquid.
  • the prills generated in downflow remain suspended at the interface between the two liquids with different densities and are driven into the second chamber where they surface and can be easily collected.
  • At least one cooling liquid has a density higher than the density of the molten urea and the dripping unit is positioned at the bottom of at least one first tank.
  • configuration in upflow indicates a configuration in which the urea drops are fed from below and solidify during their ascent towards the top.
  • the higher density of the cooling liquid with respect to the density of the molten urea determines an ascent of the latter towards the free surface of the liquid with a higher density, once delivered into said liquid.
  • At least one cooling liquid with higher density than the density of the molten urea is chosen from the group consisting of:
  • a transport unit is provided designed to move the urea granules that have risen to the surface from at least one first tank or, alternatively or additionally, means for the generation of a surface laminar flow of a cooling liquid.
  • the dripping unit in an upflow configuration is provided with means for the generation of a central pressure impulse.
  • the urea delivered takes on a toroidal bubble shape and, solidifying, generates correspondingly shaped granules.
  • At least one cooling liquid has a density higher than the density of the molten urea and the dripping unit is positioned at, preferably above, the free surface of the cooling liquid, means for generation of a surface laminar flow of the cooling liquid being provided.
  • the dripping unit comprises at least one manifold or at least one dripping tube provided with a plurality of feeding holes for feeding molten urea in the form of drops into the first tank.
  • a central needle is provided arranged for insertion of an additive in each urea drop during formation of the drop.
  • an additive for example an anti-urease substance, zinc, sulphur or other nutrients which are released once the urea granule has been consumed.
  • figure 1 is a schematic representation in lateral elevation of a first preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the downflow configuration;
  • FIG. 2 is a schematic representation in lateral elevation of a second preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the downflow configuration;
  • figure 3 is a schematic representation of a variation of the plant of figure 2;
  • FIG. 4 is a schematic representation in lateral elevation of a third preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the downflow configuration;
  • - figure 5 is a schematic representation in lateral elevation of a fourth preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the downflow configuration
  • - figure 6 is a schematic representation in lateral elevation of a fifth preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the upflow configuration
  • FIG. 7 is a schematic representation in lateral elevation of a sixth preferred embodiment of a plant for the production of solid urea in granules according to the present invention in the mixed configuration;
  • FIG. 8 is a schematic representation in section of a megaprill obtainable with the plants of figures 1 to 7.
  • a first embodiment of a plant for the production of solid urea in granules is shown, indicated overall by the number 10.
  • the plant 10 comprises a first tank 11 filled with a cooling liquid 14, immiscible with urea, and a dripper 12 from which drops 13 of molten urea are fed into the liquid through at least one feeding hole 12a.
  • the feeding hole 12a of the dripper 12 is immersed in the cooling liquid 14 to avoid freezing of the drops of molten urea 13, if they are theoretically fed into air at ambient temperature.
  • the cooling liquid 14 is preferably chosen from the fluids suitable for the food chain, in order not to alter the properties of the potentially edible urea granules.
  • suitable fluids are vegetable and edible oils, such as seed oil, soybean oil, olive oil, palm oil, and so on, mineral oils such as, for example, Vaseline oil and silicone oils.
  • Different prill diameters can be obtained depending on the density of the cooling liquid 14 into which the drops of molten urea 13 are fed and the diameter of the feeding hole 12a of the dripper 12.
  • heavy micropowders are preferably added to the cooling liquid 14 to increase the density thereof and thus obtain larger prill diameters.
  • a cooling liquid 14 is used having a density lower than the density of the molten urea so as to obtain the configuration in downflow.
  • a cooling system for cooling said cooling liquid 14 is provided.
  • the cooling system comprises a second tank 15 containing a cooling fluid 16, for example cold water, in which the first tank 11 is immersed.
  • a second embodiment of a plant for the production of solid urea in granules is shown, indicated overall by 100.
  • the plant 100 comprises a tank 110 filled with a cooling liquid 140, immiscible with urea, and a dripping unit 120 comprising at least a dripping manifold 121 immersed in the cooling liquid 140 at the free surface 141 of said liquid.
  • a reservoir 101 of molten urea is connected via a pump 102 to the dripping unit 120 to feed the latter with molten urea.
  • the manifold 121 of the dripping unit 120 is provided with a plurality of holes (not illustrated) for feeding molten urea in the form of drops into the cooling liquid 140.
  • the cooling liquid 140 has a density lower than the density of the molten urea so as to obtain the downflow configuration.
  • the drops of molten urea delivered from the dripping unit 120 solidify as they fall downwards.
  • an inclined wall 111 is provided on which, the prills 130, formed from solidification of the drops, are deposited, rolling by gravity and entrainment due to a current of cold fluid towards a transport unit 170, said current being purposely generated on the bottom of the tank.
  • the transport unit 170 comprises a perforated conveyor belt with scrapers 171, partially immersed in the tank 110 and in the cooling liquid 140, which defines a conveying path for the prills 130, from the tank 110 to a collection tank 180.
  • the conveyor scraper 171 comprises a first vertical branch 171a which transports the prills 130 outside the tank 110, and a second horizontal branch 171b along which the residual liquid left around the prills 130 is drained from the holes provided on the belt.
  • a plurality of hot air blowers 172 are also arranged for a more rapid evaporation and downward entrainment of the residual liquid and consequent drying of the prills 130.
  • the prills 130 drop by gravity into the collection tank 180.
  • the collection reservoir 180 comprises a blower 181 which completes the drying of the prills 130 collected.
  • a cooling system 150 is provided, illustrated in figure 2 only schematically, which, in general terms, comprises a withdrawing duct 151 for drawing the cooling liquid 140 from the tank 110, a cooling unit 152 outside the tank 110, a circulation pump 154 and a duct 153 for re-introduction of the liquid 140 into the tank 110.
  • the re-introduction duct 153 is arranged at the height of the inclined wall 111 in order to generate a cold current at the tank inlet which facilitates the movement of the prills towards the transport unit 170.
  • a transport unit 170' of the type illustrated in figure 3 can be provided.
  • Said transport unit 170' comprises a plurality of scrapers 17 ⁇ which, by scraping the bottom of the tank 110', convey the prills deposited there towards an inclined outlet wall 112' of the tank 110'.
  • a third embodiment of a plant for the production of solid urea in granules is shown, indicated overall by 200.
  • the plant 200 comprises a tank 210 filled with a cooling liquid 240, immiscible with urea, and a dripping unit 220 comprising a plurality of dripping ducts 221, in the figure only the head duct is shown, immersed in the cooling liquid 240 at the free surface 241 of said liquid.
  • the molten urea is fed in a controlled manner to the dripping unit 220 via a feeding unit 201 (not illustrated in detail).
  • Each duct 221 of the dripping unit 220 is provided with a plurality of feeding holes 222 for feeding molten urea in the form of drops into the cooling liquid 240.
  • the cooling liquid 240 has a density lower than the density of the molten urea so as to obtain the downflow configuration.
  • the drops of molten urea delivered from the dripping unit 220 solidify as they fall downwards, forming prills 230.
  • an inclined wall 211 is provided on which, the prills 230 formed from solidification of the drops deposit, rolling by gravity and entrainment due to a current of cold fluid towards a transport unit 270, said current being purposely generated on the bottom of the tank.
  • the transport unit 270 comprises a bucket elevator 271, partially immersed in the tank 210 and in the cooling liquid 240 which defines a conveying path for the prills, from the tank 210 to a belt conveyor 280 which transports the prills towards a collection tank (not illustrated).
  • the bucket elevator 271 comprises a first vertical branch 271a which transports the prills outside the tank 210, and a second horizontal branch 271b, at the end of which the prills drop by gravity onto the belt conveyor 280.
  • first blower 273 is provided for a first drying of the prills as they are vertically transported. Furthermore also along the second horizontal branch 271b a plurality of second blowers 272 are arranged which continue drying of the prills as they are transported horizontally.
  • the buckets 271 of the elevator are perforated in order to allow dripping during the transport and are associated with a vibration unit (not illustrated) which accelerates the dripping phase.
  • blower 281 is provided below the belt conveyor 280 which continues drying of the prills collected before reaching the tank.
  • a cooling system 250 is provided illustrated in figure 4 only schematically, which, in general terms, comprises a withdrawal duct 251 for drawing the cooling liquid 240 from the tank 210, a liquid cooling unit 252 outside the tank 210 and a re-introduction duct 253 for re-introducing the cooled liquid 240 into the tank 210.
  • the re-introduction duct 253 is arranged at the height of the inclined wall 211 in order to generate a cold current at the tank inlet which facilitates the movement of the prills 230 towards the transport unit 270.
  • a plurality of flow separating partitions 212 are provided inside the tank 210.
  • the cooling unit 250 illustrated in figure 4 further comprises a plurality of cooling plates 256 arranged inside the tank 210, above the flow separating partitions 212, and immersed in the cooling liquid 240 which control the temperature of the liquid 240 present in the upper part of the tank 210.
  • a fourth embodiment of a plant for the production of solid urea in granules is shown, indicated overall by 300.
  • the plant 300 comprises a tank 310 filled with a cooling liquid 340, immiscible with urea, and a dripping unit 320 positioned below the free surface 341 of said liquid.
  • the cooling liquid 340 has a density lower than the density of the molten urea so as to obtain the downflow configuration.
  • a first conical wall 311 is provided converging towards a lower level positioned centrally to the tank 310.
  • the prills 330 formed from the solidification of the drops roll by gravity towards said lower level, reaching a transport unit 370 positioned centrally to the tank 310.
  • the transport unit 370 has the form of a vertical screw lift and is partially immersed in the cooling liquid 340.
  • a second conical wall 375 is provided which, from the outlet 371 of the transport unit 370 positioned centrally, develops radially towards a lower level, facilitating rolling of the prills 330 towards the periphery of said surface 375.
  • an outlet 374 is provided for collection of the prills 330.
  • a fifth embodiment of a plant for the production of solid urea in granules is shown, indicated overall by 400.
  • the plant 400 comprises a tank 410 filled with a cooling liquid 440, immiscible with urea, and a dripping unit 420 comprising a plurality of dripping ducts 421, in the figure only the head duct is illustrated, immersed in the cooling liquid 440 at the bottom of the tank 410.
  • the molten urea is fed in a controlled manner to the dripping unit 420 through a feeding unit 401 (not illustrated in detail).
  • Each duct 421 of the dripping unit 420 is provided with a plurality of feeding holes 422 for feeding molten urea in the form of drops into the cooling liquid 440.
  • the cooling liquid 440 has a density higher than the density of the molten urea so as to obtain the upflow configuration.
  • a transport unit 470 is provided in the form of a conveyor belt with scrapers 471, the scrapers scraping away from the free surface 441 of the liquid, the prills 430 that have surfaced and pushes them towards a lateral side opening 472 through which the prills 430 drop into a collecting tank 480.
  • the prills 430 can be conveyed towards the outlet via a cold laminar flow of cooling liquid 440 which flows over the surface.
  • a cooling system 450 is provided only schematically shown which, in general terms, comprises a plurality of extraction elements 453 for extracting the vapours of the cooling liquid, a condenser 452 outside the tank 410 and a duct 451 for re-introducing into the tank 410 condensed cooling liquid vapours 440, therefore in liquid phase.
  • a sixth embodiment of a plant for the production of solid urea in granules is shown, indicated overall by 500.
  • the plant 500 comprises a first tank 510 filled partly with a first cooling liquid 540, immiscible with urea, having a density lower than the density of the molten urea, and partly filled with a second cooling liquid 545, immiscible with urea, having a density higher than the density of the molten urea.
  • the two cooling liquids are arranged in layers, with the liquid having a lower density 540 positioned in the upper part.
  • the first tank 510 is connected in the lower part to a second tank 550 via a connection opening 515 positioned on the bottom of both the tanks.
  • the second tank 550 is filled only with the second cooling liquid 545.
  • a system 560 for generation of a current of the second cooling liquid 545 is also provided comprising a withdrawal duct 561 for drawing the second cooling liquid 545 from the second tank 550, a pump 562 and a duct 563 for re-introduction into the first tank 510. Both the ducts 563,561 are positioned at the same level, at the bottom of the respective tank 510,550.
  • a dripping unit is also provided (not illustrated) immersed in the first cooling liquid 540 at the free surface 541 of said liquid 540.
  • the drops of molten urea delivered from the dripping unit solidify as they drop downwards, forming prills 530 which remain suspended at the boundary interface between the two phases consisting of the two cooling liquids 540,545.
  • the current generated by the respective system 560 drags the prills 530 in suspension into the second tank 550 where, due to the density lower than the second cooling liquid 545, they come to the surface.
  • a tank filled with a cooling liquid, immiscible with urea, and a dripping unit positioned at the free surface of the cooling liquid can be provided.
  • the cooling liquid used has a density higher than the density of the molten urea so as to obtain the upflow configuration and is made to flow on the surface as a laminar flow of cold liquid.
  • the drops of urea delivered from the dripping unit tend to remain on the surface, taking on a lenticular shape, and solidify due to the cold laminar flow of liquid.
  • a central needle can be provided arranged at each urea feeding hole of the dripping unit for the insertion, in each drop of urea, of an additive in the drop formation phase.
  • a prill 20 of the type illustrated in figure 8 is created in which, within the sphere of solid urea 22, a centrally positioned additive 21 is present.
  • the surface of the sphere 22 is further coated in a protective film 23 created by the drying of the cooling fluid used in the production process.
  • the dripping unit used in the plant according to the embodiment of figure 6 can be provided with means for the generation of a central pressure impulse, around which the urea delivered is distributed, generating a toroidal drop.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Fertilizers (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)

Abstract

La présente invention concerne une installation et un procédé pour la production d'urée solide en granulés. L'installation (10,100,200,300,400,500) pour la production d'urée solide dans des granules comprend au moins un premier réservoir (11,110,210,310, 410,510) pour la formation de granulés d'urée et une unité d'égouttement (12,120,220,320,420) pourvue d'au moins un trou d'alimentation (12a,222,422) pour amener de l'urée fondue sous la forme de gouttes dans le premier réservoir (11,110,210,310,410,510) et est caractérisé en ce que le premier réservoir (11,110,210,310,410,510) est rempli avec au moins un liquide de refroidissement (14,140,240,340,440,540) non miscible avec l'urée fondue.
PCT/IB2017/057385 2016-11-25 2017-11-24 Installation et procédé pour la production d'urée solide en granulés Ceased WO2018096495A1 (fr)

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CN201780072402.4A CN110267734A (zh) 2016-11-25 2017-11-24 生产颗粒状固体脲的装置与方法

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IT102016000119699 2016-11-25
IT102016000119699A IT201600119699A1 (it) 2016-11-25 2016-11-25 Impianto e processo di produzione di urea solida in granuli

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Cited By (2)

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EP4512514A1 (fr) * 2023-08-23 2025-02-26 Yara International ASA Procédé de production de particules solides comprenant de l'urée, du biuret et des composés contenant n produits pendant un procédé de condensation d'urée
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