Method for producing urea granules and plant for the implementation thereof

Abstract

A method for producing urea granules includes the following steps: a) granulating molten urea in a fluidized bed to obtain urea granules; b) separating the granules into fractions to obtain small, choice and large granules; c) cooling the large granules after step b); d) comminuting the large granules after step c) to obtain small granules; e) sending the small granules after steps b) and d) to step a); f) cooling the choice granules after step b). Before step b), the granules are cooled in a fluidized bed cooler using a flow of air that is first fed into a second section and then sent to a first section, while the granules are first fed into the first section and then sent to the second section. Also proposed is a plant for the implementation of the claimed method. The technical result consists in rendering the process for producing urea granules in a fluidized bed more environmentally friendly and efficient by reducing environmental emissions, lowering power consumption and reducing average annual steam consumption.

Description

[0001] METHOD FOR PRODUCING UREA GRANULES AND AN INSTALLATION FOR ITS IMPLEMENTATION

[0002] Field of technology

[0003] The group of inventions relates to the chemical industry, namely to the production of urea, and can be used to obtain a granulated product in a fluidized (boiling) bed.

[0004] State of the art

[0005] The prior art discloses a method for producing urea granules and an installation for its implementation (UET fluidized bed granulation technology / / New chemical technologies. Analytical portal of the chemical industry URL: s: / / newchemi strv . ru / 1 etter . php?nid= 8091 (date accessed: 04 / 26 / 2024). : / / newchemi strv. ru / 1 etter. (ID=8091, archived on 24.07.2014). The method includes the following steps:

[0006] - granulation in a fluidized bed of urea melt to obtain granules,

[0007] - cooling in a primary single-section cooler with a fluidized bed of granules after the granulation stage by means of an air flow to obtain cooled granules,

[0008] - distribution of cooled granules into fractions to obtain small, selected and large granules,

[0009] - crushing large granules to obtain small granules,

[0010] - direction of small granules after the stages of distribution and grinding to the granulation stage,

[0011] - and cooling the selected granules in a final single-section fluidized bed cooler using an air flow to obtain finished granules.

[0012] The installation for producing urea granules includes:

[0013] - a fluidized bed granulator containing means for supplying urea melt and removing granules,

[0014] - a primary cooler, including means for supplying a flow of air and granules from the granulator, as well as means for removing cooled granules,

[0015] - a granule distributor by fractions, including means for supplying cooled granules and removing small, selected and large granules, - a granule crusher, including means for supplying large granules and removing small granules,

[0016] - and a final cooler, including means for supplying selected granules, supplying an air flow and removing finished granules and removing an air flow for cleaning and emission into the atmosphere.

[0017] The granulator contains means for supplying small granules from the distributor and crusher.

[0018] The disadvantages of this solution are as follows. Cooling granules from the granulator in a single-section primary cooler requires a high air flow rate, resulting in high emissions, high energy consumption for air circulation by blowers and for heating the air, and increased moisture absorption by the granules, which degrades product quality. Cooling selected granules in a single-section final fluidized bed cooler also requires a high air flow rate, leading to similar disadvantages. Furthermore, crushing large, hot granules without the ability to pre-cool them leads to contamination of the grinder's internal components, since hot granules are softer than cold ones and, instead of breaking them into smaller fractions, are smeared across the grinder's internal surfaces.

[0019] The closest analogues include the method for producing urea granules and the installation for its implementation (Sowing the seeds of life. Stamicarbon process flow sheet for urea granulation / / ANDRITZ SEPARATION URL: s-and-fertilizers (accessed on April 26, 2024). Archived on February 7, 2023. en / industries / chemicals / agrochemicals-and- The method includes the following stages:

[0020] - granulation in a fluidized bed of urea melt to obtain granules,

[0021] - distribution of granules by fractions without a separate cooling stage, obtaining small, selected and large granules,

[0022] - cooling in a fluidized bed and grinding large granules to obtain small granules,

[0023] - direction of small granules after the stages of distribution and grinding to the granulation stage,

[0024] - and cooling of the selected granules in the final cooler using cooling water to obtain finished granules. The installation for producing urea granules includes

[0025] - a fluidized bed granulator containing means for supplying urea melt and removing granules,

[0026] - a granule distributor by fractions, including means for feeding granules from the granulator and removing small, selected and large granules,

[0027] - cooler with a fluidized bed of large granules,

[0028] - a granule crusher, including means for feeding large granules from the cooler and removing small granules,

[0029] - and a final cooler, including means for supplying selected granules and removing finished granules, as well as means for supplying and removing cooling water.

[0030] The granulator contains means for supplying small granules from the distributor and crusher.

[0031] The most similar solutions avoid the drawbacks associated with increased air consumption in the final cooler for selected pellets, as cooling water is used instead of air, and the drawbacks associated with feeding hot pellets to the crusher, thanks to the presence of a coarse pellet cooler. However, eliminating the primary pellet cooler results in an increase in the size of the final section of the pellet mill, where initial cooling occurs, complicating the pellet mill manufacturing process and increasing its material consumption. This also leads to increased air consumption in the pellet mill, supplied at higher pressure to ensure a lower pellet outlet temperature than with a separate cooler. This, among other things, leads to increased energy consumption for air pumping and air heating, increased moisture content in the pellet mill, which degrades product quality, and increased pollutant emissions.The coarse granule cooler is also a fluidized bed cooler, which, compared to a plate cooler, requires air to be supplied under the fluidization grate, supplied at higher pressure from the granulator's blower. This results in increased energy consumption and higher emissions.

[0032] Disclosure of the essence of the invention

[0033] The problem addressed by this group of inventions is the creation of a method for producing urea granules in a fluidized bed and a device for implementing it, free from the aforementioned shortcomings of all similar technologies. The technical result of this group of inventions is to improve the environmental friendliness and efficiency of the process for producing urea granules in a fluidized bed by reducing environmental emissions, lowering energy consumption, and reducing the average annual steam consumption for heating the air used in the process, while ensuring increased operational reliability of the equipment, including the granulator, large granule cooler, and grinder, while maintaining product quality.

[0034] The said result is achieved in a method for producing urea granules, comprising the stages of a) granulation in a fluidized bed of urea melt to produce urea granules, b) distribution of granules by fractions to produce small, selected and large granules, c) cooling large granules after stage b), d) grinding large granules after stage c) to produce small granules, e) directing small granules after stages b) and d) to stage a), f) and cooling selected granules after stage b).

[0035] The method includes, before step b), step g)—cooling the granules in a fluidized bed cooler having two sections, using an air flow. The air flow is first fed to the second section, after which it is directed to the first section, and the granules are first fed to the first section, after which they are directed to the second section.

[0036] From here on the designations “a)” - < <g)» даны исключительно в целях упрощения работы с материалами заявленной группы изобретений, а не обозначения последовательности осуществления действия в алфавитном порядке.

[0037] In this application, fluidized bed granulation refers to a granule production process in which a liquid phase is sprayed through nozzles onto a fluidized bed of solid particles. In this method, the solid particles of the fluidized bed are the fine granules from steps b) and d).

[0038] In this application, "selected granules" are defined as granules having a target (required) size (diameter), "fine granules" are defined as granules having a smaller size (diameter) than the selected granules, and "large granules" are defined as granules having a larger size (diameter) than the selected granules. In this application, "fluidized bed cooler" is defined as a means for cooling granules by means of an air flow passing through openings in a supporting surface (e.g., a grate or louvered fabric) on which the granules are positioned.

[0039] The use of a separate cooling stage for the granules in a counter-current two-section cooler after the granulation stage before their distribution increases the environmental friendliness and efficiency of the granule production process under consideration due to the following:

[0040] - reduction of emissions into the environment, since a lower air flow rate is required to achieve the same granule temperature as that obtained in a single-section cooler or in a granulator with an enlarged last section, and accordingly, less air emissions into the atmosphere;

[0041] - reduction of energy consumption for pumping air required to ensure the required temperature of the granules before distribution and grinding, since the described cooler requires less air, and accordingly, less energy is consumed;

[0042] - reduction in average annual steam consumption for heating the air used in the technology, which is necessary to ensure the required temperature of the granules before distribution and grinding, since the described cooler requires less air, and accordingly, less steam is consumed, and, in addition, the counter-current operating principle of the cooler ensures a deeper heat exchange between the media.

[0043] All of this ensures increased operational reliability of the equipment. For example, the granulator's size and material consumption are reduced by reducing the size of its final section and the airflow into it. Manufacturing, transportation, and on-site installation are simplified, and the operational reliability of the large granule cooler is increased by eliminating the risk of boiling process disruption, stagnant zones, and fluidized bed "sinking." Product quality is maintained and even improved, as lower air consumption for cooling introduces less moisture into the granules.

[0044] Preferably, step c) is carried out in a plate cooler.

[0045] The use of a plate cooler for cooling large granules further improves the environmental friendliness and efficiency of the granule production process under consideration due to its well-known high performance characteristics and the absence of the need for air supply, while ensuring increased operational reliability of the large granule cooler by eliminating the likelihood of disruption to the boiling process, the occurrence of stagnant zones and the "laying" of the fluidized bed.

[0046] In this application, a plate cooler (heat exchanger) is defined as a heat exchanger containing plates with openings for the inlet and outlet of warm and cold media. The plates are preferably installed substantially vertically (with a deviation from vertical of no more than 10°). Thus, product granules flow laminarly from top to bottom between the heat exchange plates under the force of gravity, cooling to the required temperature. Cooling water circulates through the interior of the heat exchange plates from bottom to top (countercurrent to the product).

[0047] The main advantage of plate coolers is the indirect cooling of bulk materials using water circulating in the enclosed space of heat exchange plates. Air is not used in the cooling process, significantly reducing costs and the environmental impact of mineral fertilizer cooling.

[0048] Preferably, the air flow is removed from step g) at a temperature of 82-94°C, while the granules after step g) have a temperature of 75-85°C.

[0049] Removing the air flow after step g)—cooling the granules in a fluidized bed cooler with two sections, with the specified parameters—as well as cooling the granules to the specified temperature, allows for more complete heat exchange between the granules and the air, thereby reducing airflow, which improves the environmental friendliness and efficiency of the granule production process. This reduces the size and material consumption of the granulator by reducing the size of its final section and the airflow entering it, simplifying its manufacturing, transportation, and on-site installation. Product quality is maintained and even improved, as lower airflow for cooling introduces less moisture into the granules.

[0050] Preferably, in step f), a coolant circulating in a closed loop is used to cool the selected granules. In the context of the present application, "a coolant circulating in a closed loop" means that the coolant circulates in a loop that does not require external replenishment of coolant.

[0051] Using a refrigerant circulating in a closed loop instead of atmospheric air improves the environmental friendliness and efficiency of the pellet production process by reducing emissions. There's no need to consume air to cool the selected pellets, resulting in fewer emissions. There's also no need to consume electricity to pump air and maintain its required temperature, nor is there any need to consume steam to heat the air.

[0052] At the same time, increased operational reliability of the equipment is ensured, including the cooler used at this stage, by eliminating the possibility of disruption of the boiling process, the formation of stagnant zones and the "laying" of a fluidized bed, and the quality of the product is maintained.

[0053] Preferably, the coolant from step f) is used to cool the large granules in step c).

[0054] Using the same refrigerant for cooling the large granules (stage c) as the selected granules (stage f) not only eliminates the need for an air flow for the same purpose but also eliminates the need for a separate closed refrigerant circuit for stage c. This improves the environmental friendliness and efficiency of the granule production process by reducing emissions and energy consumption for pumping air and cooling water. Furthermore, increased operational reliability of the equipment, including the large granule cooler, is ensured due to the absence of dynamic equipment in the unit, while maintaining product quality.

[0055] Preferably, in step c) large granules are obtained with a temperature of 55 to 60°C.

[0056] Sending large granules after cooling stage c) at the specified temperatures to grinding increases the operational reliability of the equipment, including the granule grinder, and achieves high product quality. This also further enhances the environmental friendliness and efficiency of the granule production process.

[0057] Preferably, step b) produces fine granules with a fraction of less than 2 mm, selected granules with a fraction of 2 to 5 mm, and large granules with a fraction of more than 5 mm. Obtaining granules with the specified fractions in step b) of distribution further increases the energy efficiency of the granule production process under consideration by reducing the recycling of large and small granules and increasing the percentage of selected granules. This also ensures increased operational reliability of the equipment, including the granule crusher, due to reduced load, and also ensures high product quality.

[0058] Preferably, in step g) an air blower is used to direct the air flow from the second section to the first section.

[0059] The use of an air blower at stage g) of cooling the granules in a two-section cooler further improves the environmental friendliness and efficiency of the granule production process under consideration by reusing the exhaust air from the second section, which ensures a more complete heat exchange between the media and a lower consumption of air supplied to the granulator.

[0060] The operational reliability of the equipment, including the granulator, is also further enhanced. The granulator's size and material consumption are reduced by reducing the size of its final section and the airflow entering it, simplifying its manufacturing, transportation, and on-site installation. Product quality is maintained and even improved, as lower airflow during cooling introduces less moisture into the granules, and the accompanying heating from the air blower reduces its relative humidity.

[0061] The claimed technical result is also achieved through the use of a unit for producing urea granules, including:

[0062] - a fluidized bed granulator, including means for supplying urea melt and removing urea granules,

[0063] - a granule distributor by fractions, including means for feeding granules and removing small granules into the granulator, as well as means for removing selected and large granules,

[0064] - a cooler for large granules, including means for feeding large granules from a distributor,

[0065] - a granule crusher, including means for feeding large granules from a cooler and removing small granules into a granulator,

[0066] - and a final cooler, including means for feeding selected granules from a distributor. The apparatus comprises, between the granulator and the distributor, a fluidized bed cooler, which has two sections and includes means for feeding granules from the granulator and for feeding an air flow, as well as means for removing granules from the distributor. The means for feeding granules are connected to the first section, and the means for feeding an air flow are connected to the second section. The first section includes means for feeding air from the second section, and the second section includes means for feeding granules from the first section.

[0067] The use of a counter-current two-section cooler after the granulator before the distributor increases the environmental friendliness and efficiency of the installation in question and the granule production process due to the following:

[0068] - reduction of emissions into the environment, since a lower air flow rate is required to achieve the same granule temperature as that obtained in a single-section cooler or in a granulator with an enlarged last section, and accordingly, less air emissions into the atmosphere;

[0069] - reduction of energy consumption for pumping air required to ensure the required temperature of the granules in front of the distributor and grinder, since the described cooler requires less air, and accordingly, less energy is consumed;

[0070] - reduction of steam consumption on an annual average for heating the air used in the technology, which is necessary to ensure the required temperature of the granules before the distributor and grinder, since the described cooler requires less air, and accordingly, less steam is consumed, and, in addition, the counter-current operating principle of the cooler ensures a deeper heat exchange between the media.

[0071] All of this ensures increased operational reliability of the equipment. The granulator's size and material consumption are reduced by reducing the size of its final section and the airflow entering it. Manufacturing, transportation, and on-site installation are simplified, and the operational reliability of the large-grain cooler is increased by eliminating the risk of boiling process disruption, stagnant zones, and fluidized bed "sinking." Product quality is maintained and even improved, as lower air consumption for cooling reduces moisture transfer to the granules. A plate cooler is preferred for large-grain coolers.

[0072] The use of a plate cooler for cooling large granules further improves the environmental friendliness and efficiency of the installation in question and the granule production process due to its well-known high performance characteristics and the absence of the need for air supply, while also ensuring increased operational reliability of the large granule cooler by eliminating the possibility of disruption to the boiling process, the occurrence of stagnant zones and the "laying" of the fluidized bed.

[0073] Preferably, the final cooler comprises a closed refrigerant circuit.

[0074] Using a refrigerant circulating in a closed loop instead of atmospheric air improves the environmental friendliness and efficiency of the installation and pellet production process by reducing emissions. There's no need to consume air to cool the pellets, resulting in fewer emissions. There's also no need to consume electricity to pump air and maintain its required temperature, nor is there any need to consume steam to heat the air.

[0075] At the same time, increased operational reliability of the equipment is ensured, including the final cooler used, by eliminating the possibility of disruption of the boiling process, the formation of stagnant zones and the "laying" of a fluidized bed, while the quality of the product is maintained.

[0076] Preferably, the coarse granule cooler is configured to utilize coolant from a closed coolant circulation loop of the final cooler.

[0077] Connecting the coarse granule cooler to the closed refrigerant circuit of the final cooler not only eliminates the need for an air flow for the same purpose but also eliminates the need for a separate closed refrigerant circuit for the coarse granule cooler. This improves the environmental friendliness and efficiency of the installation and the pellet production process by reducing environmental emissions and energy consumption for pumping air and cooling water. Furthermore, increased operational reliability of the equipment, including the coarse granule cooler, is ensured by the absence of dynamic equipment in the unit, while maintaining product quality. The granule size distributor is preferably designed to dispense fine granules (less than 2 mm), selected granules (2 to 5 mm), and coarse granules (more than 5 mm).

[0078] The implementation of a granule distributor with the specified capability further improves the environmental friendliness and energy efficiency of the installation in question and the granule production process by reducing the recycling of large and small granules and increasing the percentage of selected granules, while ensuring increased operational reliability of the equipment, including the granule crusher, by reducing the load, and also ensuring the quality of the product.

[0079] Preferably, the first section of the fluidized bed cooler includes means for supplying air from the second section, which includes an air blower.

[0080] The use of an air blower in the air supply means from the second section of a two-section fluidized bed cooler further improves the environmental friendliness and efficiency of the installation in question and the granule production process by reusing the exhaust air from the second section, which ensures a more complete heat exchange between the media and a lower consumption of air supplied to the granulator.

[0081] The operational reliability of the equipment, including the granulator, is also further enhanced. The granulator's size and material consumption are reduced by reducing the size of its final section and the airflow entering it, simplifying its manufacturing, transportation, and on-site installation. Product quality is maintained and even improved, as lower airflow during cooling introduces less moisture into the granules, and the accompanying heating from the air blower reduces its relative humidity.

[0082] Brief description of the drawings

[0083] The inventions are illustrated with the aid of a drawing, provided solely to illustrate embodiments of the inventions. It will be apparent to those skilled in the art that other embodiments are also possible.

[0084] The figure shows a basic process flow diagram illustrating a method and installation for producing urea granules in accordance with the claimed group of inventions.

[0085] The figure schematically shows: 1 - granulator;

[0086] 11 - feeder after granulator 1;

[0087] 12 - screen after feeder 11;

[0088] 2 - fluidized bed cooler with two sections;

[0089] 21 - first section of cooler 2;

[0090] 22 - the second section of the cooler 2;

[0091] 23 - air blower on the means of supplying air from the second section 22;

[0092] 203 - elevator;

[0093] 3 - granule distributor by fractions;

[0094] 31 - granule distributor feeder 3;

[0095] 32 - granule distributor classifier 3;

[0096] 33 - product distributor of granule distributor 3;

[0097] 302 - launch bunker;

[0098] 4 - large granule cooler;

[0099] 5 - granule crusher;

[0100] 6 - final cooler;

[0101] 61 - closed-loop refrigerant circulation refrigerator;

[0102] 7 - unit for cleaning exhaust air flows and releasing them into the atmosphere;

[0103] 71 - granulator scrubber;

[0104] 72 - cooler scrubber;

[0105] 8 - dissolution capacity.

[0106] Abbreviations in drawings: atm. air - atmospheric air.

[0107] Implementation of the invention

[0108] The proposed group of inventions is used to produce urea granules.

[0109] The method for producing urea granules is carried out using a urea production plant as follows.

[0110] The installation includes (fig.):

[0111] - a fluidized bed granulator 1 comprising means for supplying urea melt and removing urea granules. It will be obvious to a person skilled in the art that the granulator 1, in addition to the above, comprises means for supplying and removing an air flow, and the design and operating principle of the granulator 1 will also be obvious to a person skilled in the art; - a fluidized bed cooler 2 having two sections and including means for supplying granules from the granulator 1 and for supplying an air flow, as well as means for removing granules to the distributor 3. In the example of implementation presented in the figure, it is shown that after the granulator 1, the means for removing granules and their supply to the fluidized bed cooler 2 include a feeder 11 and a screen 12, which makes it possible to sift out large pieces and direct them to the dissolution tank 8.The fluidized bed cooler 2 is designed so that the means for supplying granules from the granulator 1 are connected to the first section 21 of the cooler 2, and the means for supplying an air flow are connected to the second section 22 of the cooler 2, wherein the first section 21 includes means for supplying air from the second section 21, which preferably includes an air blower 23, and the second section 22 includes means for supplying granules from the first section 21.

[0112] - a granule distributor for three fractions, including means for feeding and removing small granules (e.g., those with a fraction of less than 2 mm), selected granules (e.g., those with a fraction of 2 to 5 mm), and large granules (e.g., those with a fraction greater than 5 mm). The size range of each fraction for different production processes can be varied, which is obvious to a specialist, as long as the technology includes separation into three fractions. In the example of implementation in the figure, it is shown that after the cooler 2, the means for removing granules and feeding them to the distributor 3 include an elevator 203. And the distributor 3 contains a vibrating feeder 31, then a vibrating classifier or screen 32, as well as a product distributor 33. The product distributor 33 contains means for feeding selected and small granules from the classifier 32, means for removing small granules to the granulator 1, to the starting hopper 302 or to the dissolution tank 8, as well as means for removing selected granules to the granulator 1, to the starting hopper 302 or to the final cooler 6.And classifier 32, in addition to the above, contains means for removing large granules into a large granule cooler 4;.

[0113] - the said large granule cooler 4, which obviously comprises means for feeding large granules from the distributor 3, preferably from the classifier 32, and for removing them, as well as means for feeding and removing a cooling medium (not shown in the figure). The cooler 4 is, in the preferred embodiment, a plate cooler, but other embodiments are possible;

[0114] - a granule crusher 5, including means for feeding large granules from a cooler 4 and removing small granules into a granulator 1. According to a preferred embodiment, the crusher 5 is a crushing unit containing bins and roller crushers;

[0115] - and a final cooler 6, including means for supplying selected granules, as well as means for supplying and removing a cooling medium. In the preferred embodiment shown in the figure, the final cooler is a plate cooler with a closed coolant circuit, primarily water, comprising a cooler 61 and a blower. Cooler 6 may also include means for supplying and removing an air flow to dedust the selected granules before their removal as a marketable product.

[0116] The exhaust air flows are fed to the treatment units 7, such as scrubbers, via appropriate exhaust means. Due to the reduction in air consumption in the process and the reduction in energy consumption for its supply, the energy consumption required for feeding the exhaust air to the treatment units 7, as well as for the operation of other units associated with the units 7, is also reduced. In the preferred embodiment, the figure shows that the air exhaust means from the granulator 1 are connected to the scrubber 71, and the air exhaust means from the granule cooler 2 and the final cooler of the selected granules 6 are connected to the scrubber 72. The necessary means and methods for organizing the operation of the units 7, in particular, scrubbers 71-72, will be obvious to a person skilled in the art. After the units 7, the air can be discharged into the atmosphere.

[0117] In addition, in a preferred embodiment (not shown in the figure), the large granule cooler 4 is connected to a closed circuit for the circulation of the coolant of the final cooler 6.

[0118] All the mentioned means for supplying and removing granules, air flows, and urea include any known and necessary elements to ensure the operability of the installation: pipelines, connectors, blowers, and other standard and obvious elements.

[0119] In general, the selection and placement of each specific equipment, material, element or environment will be clear to a specialist in this field of technology based on the specified conditions and parameters of the process flow diagram for obtaining urea.

[0120] The plant operates and the method is carried out according to the preferred embodiment as follows. Stage a) is fluidized bed granulation of urea melt to produce urea granules. Urea melt at a temperature of 134-140°C is fed to the distribution manifolds of granulator 1. Granulator 1 comprises several compartments housing melt nozzles and one cooling compartment supplied with cooling air only. The melt is sprayed through the nozzles into a fluidized bed of granulated urea. As the granules move through the granulation section, their size gradually increases due to multiple layering and crystallization of urea melt films. Atomization air is supplied to the nozzles from the atmosphere by an atomization fan. The air is preheated in a spray heater to prevent urea crystallization in the spray nozzles and discharge pipelines.For winter operation, preheating of the spray air is provided in the spray preheater.

[0121] Fluidization air is supplied by a fan to all compartments of granulator 1 through separate air ducts and distributed evenly through a perforated grille. In the first granulation compartments, the air is preheated in a preheater. This preheating is necessary to maintain an optimal granulation temperature of 104-108°C. For winter operation, preheating of the fluidization air is provided in the granulator's preheater.

[0122] In the final cooling section, the temperature of the granules is reduced to 85-95 °C and they are unloaded from the granulator 1 using vibrating feeders 11. The granules from the vibrating feeders 11 enter screens 12, where large particles and agglomerates larger than 10 mm are removed and fed to the dissolution tank 8.

[0123] The recycling of small granules to be processed is introduced into the first section of granulator 1. The exhaust air with urea dust is removed from granulator 1 and sent to scrubber 71, the operating principle of which is obvious and understandable to a specialist; in addition, a schematic embodiment of scrubber 71 is shown in the figure.

[0124] Stage g) – cooling of the granules in a two-section fluidized bed cooler using an air flow. After screens 12, the granules are fed into a two-section fluidized bed cooler 2, where their temperature is reduced to 75-85°C for further distribution, as well as for additional cooling and grinding (crushing). Cooling is achieved by contact with a fluidized air flow supplied from the atmosphere under the working grate of each section 21, 22 by a fan. In this case, the air flow is first fed into the second section 22, then by means of the air blower 23 from the second section 22 into the first 21, and the granules are first fed into the first section 21, then from the first 21 into the second section 22. For the winter operating mode, preliminary heating of the air flow in the pre-heater is provided, and due to the design of the cooler 2 in two sections, the volume of heated air and the flow rate of the coolant are lower.

[0125] The air flow after cooler 2 is discharged at a temperature of 82-94°C to treatment units 7, specifically scrubber 72, where it is cooled and cleaned before being discharged to the atmosphere. The operating principle of scrubber 72 is clear and understandable to a specialist. Furthermore, a schematic embodiment of scrubber 72 is shown in the figure.

[0126] Stage b) – granule distribution by fraction, producing fine, select, and coarse granules. After cooler 2, the granules are directed into the receiving bins of bucket elevators 203, where they are lifted upward for distribution by fraction. Next, the granules in distributor 3 are uniformly fed by vibrating feeders 31 into vibrating screens 32. Passing through the screens of screens 32, the granules are distributed into the following fractions:

[0127] - large granules, fractions larger than 5 mm, are separated on the upper sieve and sent for cooling, and then to the crusher bins and further to the crushers 5 (crusher 5);

[0128] - selected (commercial) granules, fractions of 2 to 5 mm in size, are passed through the upper sieve, separated on the lower sieve and through the product distributor 33 are discharged into the final cooler 6;

[0129] - small granules, fractions smaller than 2 mm, are passed through the upper and lower sieves and returned to the granulator 1 through the product distributor 33.

[0130] The product distributor 33 allows the selected (commercial) granules to be directed, in addition to the final cooler 6, into the starting hopper 302 or into the granulator 1, and also allows the fine fraction to be directed, in addition to the granulator 1, into the starting hopper 302 or into the dissolution tank 8.

[0131] Stage c) — cooling of large granules after stage b). Large urea granules are diverted to plate cooler 4 for large granules, where their temperature is reduced to 55-60°C. Cooler 4 uses a coolant circulating in the closed circuit of final cooler 6 for selected granules, used in stage 0. Stage d) — crushing of large granules after stage c) to obtain small granules. After cooler 4, the granules are diverted for crushing, namely, to crusher bins and then to roller crushers 5 (crusher 5). Due to the lower temperature in crusher 5, the granules split better and do not stick to the crusher rolls, which increases the operational reliability of the equipment and its operating efficiency.

[0132] Stage e) - direction of small granules after stages b) and d) to stage a). The granules obtained in the grinder 5 are mixed with small granules from the product distributor 33 and directed to the granulator 1 as seed particles.

[0133] Start-up hopper 302 is designed to store product used as recycle for starting granulator 1. Seed particles from start-up hopper 302 are discharged into bucket elevators 203 and sent through distributor 3 to granulator 1 to provide the initial amount of recycle for the plant. Start-up hopper 302 is filled with product using selected or fine granules from product distributor 33.

[0134] Stage f) – cooling of the selected granules after stage b). The selected granules of the required size are sent from the product distributor 32 for final cooling to a temperature of no more than 40°C to the final cooler 6, in which the granules are cooled by a closed coolant circulation loop, namely cooling water, due to heat transfer through the wall of the thermal plates circulating within them by a pump. To relieve the heat load and cool the water, a cooler 61 is provided in the loop, using recycled water as a coolant. Dust removal purge air is supplied to the final cooler 6 by a fan, which is conditioned in a dehumidifier to reduce humidity and prevent moisture condensation on the surface of the granules. The air is then discharged into a scrubber 72.

[0135] The finished product in the form of cooled selected granules is sent by conveyor to a warehouse or shipment.

[0136] The essence of the invention is confirmed by examples, which are particular cases of the implementation of the invention, but do not limit it.

[0137] As can be seen, the same flow rate of urea melt fed to granulator 1, its temperature, the pressure of fluidization air fed to granulator 1, its temperature, as well as the product yield in the form of granules after cooler 6 and their quantity were adopted for all the examples considered. All examples are summarized in Table 1 below.

[0138] A well-known example (prototype).

[0139] Urea granules are obtained using the technology of the closest analogue as follows:

[0140] - urea melt is fed into granulator 1 in the amount of 129 107 kg / h and at a temperature of 139.5°C;

[0141] - fluidized air is supplied to granulator 1 in the amount of 723,000 kg / h with a temperature of 37.6°C and a pressure of 8.0 kPa;

[0142] - the obtained granules are sent to distribution 3 with a temperature of 80°C;

[0143] - large granules after distribution 3 are cooled in a cooler 4 with a fluidized bed to a temperature of 57.5°C;

[0144] - fluidized air is supplied to cooler 4 in the amount of 25,500 kg / h with a temperature of 37.6°C and a pressure of 8.0 kPa from the granulator blower;

[0145] - selected granules in the amount of 126,800 kg / h after distribution 3 are cooled in the final cooler 6 to a temperature of 40°C;

[0146] - the power consumption for pumping air into granulator 1 and cooler 4 is 1621 kW;

[0147] - the power consumption for air suction in the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 1404 kW;

[0148] - the gross emission of pollutants from the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 75.4 kg / h;

[0149] - steam consumption for heating air for granulator 1 and for cooler 4 in winter at an atmospheric air temperature of minus 30°C is 23,830 kg / h;

[0150] Example 1.

[0151] The production of urea granules is carried out in accordance with the above-described embodiment of the invention, wherein:

[0152] - urea melt is fed into granulator 1 in the amount of 129 107 kg / h and at a temperature of 139.5°C;

[0153] - fluidized air is supplied to granulator 1 in the amount of 613,500 kg / h with a temperature of 37.6°C and a pressure of 8.0 kPa;

[0154] - the obtained granules are discharged into a two-section fluidized bed cooler 2 with a temperature of 90°C; - an air flow with a temperature of 32.4°C, a pressure of 2.5 kPa and an amount of 64,200 kg / h is fed into cooler 2;

[0155] - air flow with a temperature of 88.9°C is removed from cooler 2;

[0156] - from cooler 2, granules are diverted to distribution 3 at a temperature of 80°C;

[0157] - large granules after distribution 3 are cooled in cooler 4 to a temperature of 57.5°C;

[0158] - selected granules in the amount of 126,800 kg / h after distribution 3 are cooled in the final cooler 6 to a temperature of 40°C;

[0159] - the power consumption for pumping air into granulator 1 and cooler 2 is 1425 kW;

[0160] - the power consumption for air suction in the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 1290 kW;

[0161] - the gross emission of pollutants from the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 68.3 kg / h;

[0162] - steam consumption for heating air for granulator 1 and for cooler 2 in winter at an atmospheric air temperature of minus 30°C is 21,575 kg / h.

[0163] Example 2.

[0164] The production of urea granules is carried out in accordance with the above-described embodiment of the invention, wherein:

[0165] - urea melt is fed into granulator 1 in the amount of 129 107 kg / h and at a temperature of 139.5°C;

[0166] - fluidized air is supplied to granulator 1 in the amount of 577,000 kg / h with a temperature of 37.6°C and a pressure of 8.0 kPa;

[0167] - the obtained granules are transferred to a two-section fluidized bed cooler 2 with a temperature of 95°C;

[0168] - a flow of air with a temperature of 32.4°C, a pressure of 2.5 kPa and a quantity of 59,000 kg / h is supplied to cooler 2;

[0169] - air flow with a temperature of 93.9°C is removed from cooler 2;

[0170] - from cooler 2, granules are diverted to distribution 3 at a temperature of 85°C;

[0171] - large granules after distribution 3 are cooled in cooler 4 to a temperature of 60°C;

[0172] - selected granules in the amount of 126,800 kg / h after distribution 3 are cooled in the final cooler 6 to a temperature of 40°C; - the power consumption for pumping air into the granulator 1 and into the cooler 2 is 1339 kW;

[0173] - the power consumption for air suction in the unit for cleaning exhaust air flows and emitting into the atmosphere 7 is 1219 kW;

[0174] - the gross emission of pollutants from the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 64.1 kg / h;

[0175] - steam consumption for heating air for granulator 1 and for cooler 2 in winter at an atmospheric air temperature of minus 30°C is 20,258 kg / h.

[0176] Example 3.

[0177] The production of urea granules is carried out in accordance with the above-described embodiment of the invention, wherein:

[0178] - urea melt is fed into granulator 1 in the amount of 129 107 kg / h and at a temperature of 139.5°C;

[0179] - fluidized air is supplied to granulator 1 in the amount of 657,500 kg / h with a temperature of 37.6°C and a pressure of 8.0 kPa;

[0180] - the obtained granules are transferred to a two-section fluidized bed cooler 2 with a temperature of 85°C;

[0181] - a flow of air with a temperature of 32.4°C, a pressure of 2.5 kPa and a quantity of 69,600 kg / h is supplied to cooler 2;

[0182] - air flow with a temperature of 81.9°C is removed from cooler 2;

[0183] - from cooler 2, granules are diverted to distribution 3 at a temperature of 75°C;

[0184] - large granules after distribution 3 are cooled in cooler 4 to a temperature of 55°C;

[0185] - selected granules in the amount of 126,800 kg / h after distribution 3 are cooled in the final cooler 6 to a temperature of 40°C;

[0186] - the power consumption for pumping air into granulator 1 and cooler 2 is 1528 kW;

[0187] - the power consumption for air suction in the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 1373 kW;

[0188] - the gross emission of pollutants from the unit for cleaning exhaust air flows and releasing them into the atmosphere 7 is 73.3 kg / h;

[0189] - steam consumption for heating air for granulator 1 and for cooler 2 in winter at an atmospheric air temperature of minus 30°C is 23,135 kg / h. Table 1. Examples of the invention and an example of the closest analogue (prototype).

[0190] Thus, the use of this group of inventions improves the environmental friendliness and efficiency of the fluidized bed urea granulation process by reducing environmental emissions, lowering energy consumption, and reducing the average annual steam consumption for heating the air used in the process, while ensuring increased operational reliability of the equipment, including the granulator, large granule cooler, and crusher, while maintaining product quality. The granulator's size and material consumption are also reduced by reducing the size of its final section and the air flow entering it, simplifying its manufacturing, transportation, and on-site installation.

Claims

Invention formula 1. A method for producing urea granules comprising the steps of a) granulation in a fluidised bed of urea melt to produce urea granules, b) distributing the granules into fractions to produce small, selected and large granules, c) cooling the large granules after step b), d) grinding the large granules after step c) to produce small granules, e) directing the small granules after steps b) and d) to step a), f) and cooling the selected granules after step b), characterised in that before step b) it comprises the step of g) cooling the granules in a fluidised bed cooler having two sections by means of an air flow, wherein the air flow is first fed into the second section, after which it is directed into the first section, and the granules are first fed into the first section, after which they are directed into the second section.

2. The method according to item 1, characterized in that stage c) is carried out in a plate cooler.

3. The method according to item 1, characterized in that the air flow is removed from stage g) at a temperature of 82-94°C, while the granules after stage g) have a temperature of 75-85°C.

4. The method according to item 1, characterized in that at stage f) a coolant circulating in a closed circuit is used to cool the selected granules.

5. The method according to item 4, characterized in that the coolant from step f) is used to cool the large granules in step c).

6. The method according to item 1, characterized in that at stage c) large granules with a temperature of 55 to 60°C are obtained.

7. The method according to item 1, characterized in that at stage b) small granules with a fraction of less than 2 mm, selected granules with a fraction of 2 to 5 mm, and large granules with a fraction of more than 5 mm are obtained.

8. The method according to claim 1, characterized in that at step g) an air blower is used to direct the air flow from the second section to the first section.

9. An installation for producing urea granules, comprising a fluidized bed granulator, including means for supplying urea melt and removing urea granules, SUBSTITUTE SHEET (RULE 26) a granule distributor by fractions, including means for feeding granules and removing small granules into a granulator, as well as means for removing selected and large granules, a cooler for large granules, including means for feeding large granules from the distributor, a granule crusher, including means for feeding large granules from the cooler and removing small granules into the granulator, and a final cooler, including means for feeding selected granules from the distributor, characterized in that it contains between the granulator and the distributor a fluidized bed cooler, having two sections and including means for feeding granules from the granulator and for feeding an air flow, as well as means for removing granules into the distributor, wherein the means for feeding granules are connected to the first section, and the means for feeding an air flow are connected to the second section, wherein the first section includes means for feeding air from the second section, and the second section includes means for feeding granules from the first section.

10. The installation according to item 9, characterized in that the cooler for large granules is a plate cooler.

11. The installation according to item 9, characterized in that the final cooler contains a closed refrigerant circulation circuit.

12. The installation according to item 11, characterized in that the large granule cooler is designed with the possibility of using coolant from a closed coolant circulation circuit of the final cooler.

13. The installation according to item 1, characterized in that the granule distributor by fraction is designed with the possibility of dispensing small granules with a fraction of less than 2 mm, selected granules with a fraction of 2 to 5 mm, and large granules with a fraction of more than 5 mm.

14. The installation according to item 9, characterized in that the first section of the fluidized bed cooler includes means for supplying air from the second section, which includes an air blower. SUBSTITUTE SHEET (RULE 26)

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