Energy-optimized granulation method for urea-containing particles and fluidized bed granulator system
A two-stage cooling process using a fluidized bed cooler and bulk flow cooler optimizes the energy efficiency of urea-containing particle granulation by minimizing energy input and maintaining optimal temperatures, addressing inefficiencies in existing systems.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- THYSSENKRUPP FERTILIZER TECH GMBH
- Filing Date
- 2024-03-26
- Publication Date
- 2026-04-22
AI Technical Summary
Existing fluidized bed granulation systems for urea-containing particles face energy inefficiencies due to the high energy input required for cooling, which is exacerbated by high ambient temperatures and high product loads, leading to reduced manufacturing capacity and product quality.
A two-stage cooling process using a fluidized bed cooler and a bulk flow cooler, where urea-containing particles are initially cooled to 80°C to 108°C within the fluidized bed granulator and then further cooled to 30°C to 50°C using a bulk flow cooler with cooling water, minimizing energy input and optimizing the granulation process.
The method reduces energy consumption by leveraging indirect heat transfer with cooling water, maintaining optimal particle temperatures for efficient granulation and reducing construction costs through lower fan and filter requirements, while enhancing product quality and capacity.
Smart Images
Figure 2026513036000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an energy-optimized granulation method for urea-containing particles in a fluidized bed granulator system.
[0002] The present invention further relates to a fluidized bed granulator system for the energy-optimized granulation of urea-containing particles.
Background Art
[0003] As a result of the continuous increase in the world population, there is an ongoing need for reliable, easy-to-manufacture, and inexpensive fertilizers. These conventional fertilizers may contain nitrogen, phosphates, sulfur, calcium, selenium, potassium, or micronutrients. A commonly used general fertilizer contains urea as a main component. Water-soluble urea is rapidly decomposed in the soil along with the formation of ammonia and nitrate compounds. Depending on the use, the fertilizer may contain only urea or a combination of urea and one or more of the above components, such as phosphates, sulfur, potassium, or micronutrients.
[0004] Urea can be produced on a large industrial scale by reacting ammonia with carbon dioxide in the following (simplified) two-step reaction.
Chemical Formula
[0005] These problems can be avoided by using a fluidized bed granulation process, which results in harder, more stable, and more homogeneous granules. The resulting granular urea is particularly suitable for bulk mixtures. Furthermore, there is less demixing or mechanical damage when mixing and transporting urea-containing fertilizers. The size, size distribution, geometric shape, and mechanical properties of the final product depend heavily on the temperature during the granulation process. Therefore, a controlled temperature environment is essential to achieve reproducible granular products with consistent product characteristics, such as hardness, caking, or dust formation.
[0006] Fluidized bed granulator systems rely heavily on the use of ambient air for cooling. Therefore, the capacity of a fluidized bed granulator can be limited by the ambient air temperature or the amount of heat that can be dissipated by the ambient air. This can lead to high temperatures within the plant, which can reduce the amount of product that can be manufactured or result in reduced product quality and degraded operating conditions. Furthermore, under certain operating conditions (e.g., very high product loads), the granulation temperature can become too high. This is especially true when the system operates at high capacity, high ambient temperatures, or both. Additionally, many systems already incorporate fluidized bed coolers to reduce the granular temperature from approximately 95°C to 60-70°C. This requires a large amount of ambient air, which can also be problematic under the operating conditions mentioned above.
[0007] Cooling urea-containing particles involves a significant energy input to provide cooling air. Furthermore, it is crucial to cool the urea-containing particles at a time favorable to the process in order to enable the design of the method as efficiently as possible. [Overview of the Initiative] [Problems that the invention aims to solve]
[0008] Therefore, the object of the present invention is to provide an energy-optimized granulation method and fluidized bed granulator system for urea-containing particles in which the energy required to cool the urea-containing particles is minimized, and the method and operation of the fluidized bed granulator system are optimized for the process. [Means for solving the problem]
[0009] This objective is first achieved in the present invention by the feature of the feature portion of claim 1, wherein after granulation, the urea-containing particles are cooled to a temperature in the range of 80°C to 108°C in the cooling zone of a fluidized bed granulator, and after preliminary screening, at least a portion of the urea-containing particles are cooled to a temperature in the range of 30°C to 50°C by a bulk flow cooler in a second step.
[0010] The cooling zone can be a fluidized bed cooler, which can achieve air cooling of urea-containing particles by a blower. To save capital costs, the fluidized bed cooler is located in the fluidized bed granulator. Because the energy input for compressing the cooling air is relatively high, in this invention, the urea-containing particles are cooled to a temperature of 80°C to 108°C within the cooling zone. The urea-containing particles exit the fluidized bed granulator / granulation zone within the fluidized bed granulator at a temperature exceeding 100°C. Therefore, the cooling output in the cooling zone is energetically lower compared to the cooling in the second step.
[0011] A bulk flow cooler should be understood as a heat exchanger in which the product to be cooled can flow relatively smoothly between welded heat exchanger plates according to the "first-in, first-out" principle. On the other side of the plates, there is a flow of cooling water at the appropriate temperature. This indirect heat transfer method minimizes the need for fans, bag filters, or scrubbers. This makes it possible to provide a cost-effective solution not only for cooling bulk materials but also for heating them. Furthermore, the cooling operation itself has no exhaust.
[0012] The bulk flow cooler cools urea-containing particles or a portion of urea-containing particles, i.e., the portion that enters the bulk flow cooler after preliminary screening, to a temperature of 30°C to 50°C. Therefore, the bulk flow cooler accounts for the majority of the cooling output, and the cooling output generated by the cooling zone of the fluidized bed granulator is lower in comparison to the cooling output of the bulk flow cooler. Cooling with a bulk flow cooler using appropriate cooling water is more energy-efficient than cooling the fluidized bed with compressed air, and as a result, the overall energy requirements of the fluidized bed granulator system are minimized.
[0013] In particular, cooling water in urea plants is generally readily available at appropriate temperature levels (e.g., 30 / 40°C for both forward and return paths) and is significantly cheaper than the electrical energy required to compress cooling air.
[0014] Further preferred configurations of the present invention arise from other features specified in the dependent claims.
[0015] In the first configuration of the present invention, a two-stage preliminary screening is provided, in which urea-containing particles having a particle size greater than 10 mm are separated first, and then urea-containing particles having a particle size greater than 4 mm are separated. The product exits the fluidized bed granulator with a relatively wide particle size range of about 0.5 to 10 mm or more. Therefore, having a two-stage preliminary screening may be advantageous, as larger particles are separated first, and then so-called "crude material," i.e., particles having a particle size greater than 4 mm but less than 10 mm, are separated.
[0016] Furthermore, in a further configuration of the method of the present invention, after separation, urea-containing particles having a particle size greater than 4 mm but less than 10 mm are cooled and pulverized, and the cooled and pulverized urea-containing particles then enter a fluidized bed granulator. The coarser fraction, i.e., the crude material, is present in the product in only a small proportion in terms of quantity. The requirements of the screen used to separate the crude material, i.e., the urea-containing particles greater than 4 mm but less than 10 mm, are relatively low because the majority of particles with smaller particle sizes pass through. Therefore, the amount of urea wear or clogging during operation is small.
[0017] After grinding, the urea-containing particles can be returned to a fluidized bed granulator, for example, by a bucket conveyor, and as a result, the ground urea-containing particles can undergo further granulation.
[0018] In a particularly advantageous configuration of the method of the present invention, urea-containing particles having a particle size greater than 4 mm but less than 10 mm are entered into a fluidized bed granulator by pneumatic conveying. The advantage of pneumatic conveying or a pneumatic conveying system for returning the particles to the fluidized bed granulator is that a bucket conveyor, which is common in the prior art, is not required. This means that the building height can be kept low, and it only needs to be equal to the height of the bulk flow cooler. The conveying airflow required for dense phase transport is a pressure of about 1-2 bar, about 100°C, and a volume of less than 1% of the fluidized air in the fluidized bed granulator.
[0019] To facilitate further processing of urea-containing particles having a particle size greater than 4 mm and less than 10 mm, a further configuration of the method of the present invention provides cooling the separated particles to about 65°C. The temperature of "about 65°C" can be, for example, 50°C to 80°C, and especially 60°C to 70°C. When the crude material is to be further processed or ground, it is advantageous to pre-cool the particles to avoid urea abrasion and clogging.
[0020] For this purpose, in a more advantageous configuration of the present invention, the separated particles can be pulverized by a roller pulverizer. For the roller pulverizer, the optimal temperature for urea-containing particles is 65°C.
[0021] A further configuration of the method of the present invention may provide that, after preliminary screening, urea-containing particles having a particle size of less than 4 mm are subjected to dust removal. Dust removal can be carried out according to any suitable method known from the prior art.
[0022] In a practical variant of the particle transport, in a further configuration of the method, urea-containing particles having a particle size of less than 4 mm are transported to the bulk flow cooler by a bucket conveyor. In the case of urea-containing particles of less than 4 mm, both on-size product (2 - 4 mm) of the target size and fines (less than 2 mm) still to be separated are present after preliminary screening. The bucket conveyor enables the transport of the urea-containing particles to the bulk flow cooler, and the particles pass from top to bottom with the aid of gravity. This bucket conveyor can be arranged at a lower level in the construction of the fluidized bed granulation system for screening and returning fines, and thus does not need to be as high as customary in conventional designs known from the prior art. Thereby, the construction cost of the steel structure in the construction can be minimized.
[0023] To achieve the desired particle size, in a further configuration of the method of the present invention, after cooling the urea-containing particles to a temperature within the range of 30 °C to 50 °C, the urea-containing particles having a particle size of less than 2 mm are separated. Accordingly, a suitable fine screen arranged downstream of the bulk flow cooler operates within the temperature range of 30 - 50 °C, and thus the urea-containing particles are optimally protected from urea wear or clogging since they are already cooled and hardened.
[0024] In a particularly advantageous configuration of the method of the present invention, the separated particles having a particle size of less than 2 mm enter the fluidized bed granulator. The discharge of fines is at a level lower than that of the fluidized bed granulator. Accordingly, one option for transporting the fines is to use a bucket conveyor.
[0025] In a further preferred configuration of the present invention, the separated particles having a particle size of less than 2 mm can enter the fluidized bed granulator by air conveyance. Similar to the coarse material, the air conveyance or air conveyance system for returning the particles to the fluidized bed granulator has the advantage that a bucket conveyor, which is customary in the prior art, is not required. This means that the height of the building can be kept low and it is only necessary to equal the height of the bulk flow cooler.
[0026] For dense-phase conveying, the conveying air flow required is a pressure of about 1 to 2 bar, a temperature of about 100 °C, and a volume less than 1% of the fluidizing air of the fluidized bed granulator. Further, since the cooled fine powder, i.e., urea-containing particles less than 2 mm, can be supplied to different chambers of the fluidized bed granulator at a temperature slightly exceeding 45 °C, it can have a beneficial effect on the energy balance of the fluidized bed granulator.
[0027] The above object is also achieved by a fluidized bed granulator system for energy-optimized granulation of urea-containing particles, comprising the following elements operably connected to each other.
[0028] a) A fluidized bed granulator for granulating urea-containing particles, b) A cooling zone disposed within the fluidized bed granulator for cooling the urea-containing particles to a temperature within the range of 80 °C to 108 °C using air, c) A preliminary screening device for separating overly large urea-containing particles having a particle size preferably greater than 4 mm after granulation, d) A cooling device for cooling the urea-containing particles to a temperature within the range of 30 °C to 50 °C, the cooling device comprising at least one bulk flow cooler, e) A screening device for separating overly small urea-containing particles having a particle size preferably less than 2 mm.
[0029] The fluidized bed granulator system may, in particular, include a fluidized bed granulator configured and adapted to granulate urea-containing particles, the fluidized bed granulator having a cooling zone configured and adapted to cool the urea-containing particles to a temperature in the range of 80°C to 108°C with air. The fluidized bed granulator system may also include a preliminary screening device configured and adapted to separate urea-containing particles having a particle size of preferably more than 4 mm in order to separate excessively large urea-containing particles after granulation, and a cooling device configured and adapted to cool the urea-containing particles to a temperature in the range of 30°C to 50°C and having at least one bulk flow cooler. Finally, the fluidized bed granulator system may include a screening device configured and adapted to separate urea-containing particles having a particle size of preferably less than 2 mm in order to separate excessively small urea-containing particles, the screening device being located downstream of the bulk flow cooler 4.
[0030] In the first configuration of the fluidized bed granulator system of the present invention, the preliminary screening device comprises at least two screens, the first screen enabling the separation of urea-containing particles having a particle size greater than 10 mm, and the second screen enabling the separation of urea-containing particles having a particle size greater than 10 mm and less than 4 mm.
[0031] A more advantageous configuration of the fluidized bed granulator system of the present invention provides an air conveyor that enables the transport of separated urea-containing particles having particle sizes greater than 10 mm and less than 4 mm to the fluidized bed granulator, and / or an air conveyor that enables the transport of separated urea-containing particles having particle sizes less than 2 mm to the fluidized bed granulator.
[0032] In a further configuration of the fluidized bed granulator system of the present invention, the fluidized bed granulator system is designed and configured to carry out the method of the present invention. The above description of the method of the present invention is also applicable to the fluidized bed granulator system of the present invention with necessary modifications.
[0033] The various embodiments of the present invention referred to in this patent application can be advantageously combined with one another unless otherwise specified in each individual case.
[0034] The present invention will be described below in exemplary embodiments with reference to the relevant drawings. [Brief explanation of the drawing]
[0035] [Figure 1] This is a schematic diagram of a conventional fluidized bed granulator system optimized in terms of capital cost. [Figure 2] This is a schematic diagram of a fluidized bed granulator system according to an exemplary embodiment of the fluidized bed granulator system of the present invention. [Figure 3] This figure shows a schematic configuration of a fluidized bed granulator system according to a particularly preferred exemplary embodiment. [Modes for carrying out the invention]
[0036] Figure 1 shows an exemplary schematic diagram of a prior art fluidized bed granulator system 1. The fluidized bed granulator system 1 comprises a fluidized bed granulator 3 and a cooling zone 2 located within or connected to the fluidized bed granulator 3. The term “connected” generally refers to connecting means capable of / suitable for transporting or transferring process fluids, solids or gases and / or mixtures thereof, such as pipes, ducts, pumps and hoses, and further includes tanks, containers and / or pumps. This definition includes connecting means suitable for gases, solids and liquid media under low pressure (less than 1 bar), and gases, solids and liquid media under high pressure (greater than 1 bar, preferably up to 10 bar).
[0037] In the cooling zone, the particles are cooled to a temperature range of less than 70°C and then enter a screening device 9 connected to the cooling zone 2. The screening device 9 separates the granular particles from the fluidized bed granulator 3 into product particles of the appropriate size within the desired product size, oversized particles (exceeding the desired product size), and undersized particles (below the desired product size). Furthermore, a preliminary screening device 7 is provided to separate particles with a particle size much larger than that of the oversized particles. These "clumps" are removed from the process and enter a recovery container 10. Further urea-containing particles enter the screening device 9 by a bucket conveyor 6.
[0038] The structure of the screening device 9 comprises a first screen 11 having a mesh size greater than the desired particle size and a second screen 12 having a particle size less than the desired particle size, and the screens divide the screening device 9 into three parts. The screening device 9 further includes outputs 13 of the final product particles between the first screen 11 and the second screen 12, for example, an output 14 of oversized particles above the first screen 11 and an output 15 of undersized particles below the second screen 12. The output 15 of the undersized particles is connected to the fluidized bed granulator 1 via a first return inlet 16, and the output 14 of the oversized particles is connected to the fluidized bed granulator 1 via a roller grinder 5 or similar device that produces pulverized particles.
[0039] The final product particles are sent from the screening device 9 to the cooler 17 for final curing and cooling. The final product (not shown here) can then be packaged or otherwise processed.
[0040] Figure 2 shows a schematic diagram of the fluidized bed granulator system 1 according to an exemplary embodiment of the fluidized bed granulator system 1 of the present invention. The cooling zone 2 within the fluidized bed granulator 3 is kept as small as possible compared to the prior art, and as a result, urea-containing particles exit the fluidized bed granulator 3 / cooling zone 2 at a temperature in the range of 80°C to 108°C. Furthermore, a preliminary screening device 7 is provided to separate particles having a particle size much larger than that of oversized particles. These "clumps" are removed from the process and enter a recovery container 10. Further urea-containing particles enter a screening device 9 by a bucket conveyor 6. However, the preliminary screening device 7 also includes an additional first screen 11 that separates oversized particles from product particles and undersized particles.
[0041] Oversized particles, being less numerous than the rest of the urea-containing particles, are then passed through a recirculation cooler 18, crushed in a roller crusher 5, and returned to the fluidized bed granulator 3 by an air conveyor 19. If the crude material is to be further processed or crushed, it is advantageous to pre-cool the particles to avoid urea abrasion and clogging.
[0042] In this exemplary embodiment, a dust removal unit 20 is further provided, which can remove undersized particles and product particles from the flow after preliminary screening.
[0043] Downstream of the preliminary screening device 7, undersized particles and product particles enter a cooling device 8, which includes a bulk flow cooler 4. In the bulk flow cooler 4, the undersized particles and product particles are cooled to a temperature in the range of 30-50°C. The air conveyor 19 for returning the particles to the fluidized bed granulator 3 has the advantage of not requiring a bucket conveyor, which is common in the prior art. This means that the building height can be kept low, and it only needs to be equal to the height of the bulk flow cooler 4.
[0044] The bulk flow cooler 4 cools the urea-containing particles or a portion of the urea-containing particles, i.e., the portion that enters the bulk flow cooler 4 after preliminary screening, to a temperature of 30°C to 50°C. Therefore, the bulk flow cooler 4 accounts for the majority of the cooling output, and the cooling output provided by the cooling zone 2 is lower in comparison to the cooling output of the bulk flow cooler 4. Cooling by the bulk flow cooler 4 using appropriate cooling water is more energy-efficient than cooling the fluidized bed with compressed air, and as a result, the overall energy requirements of the fluidized bed granulator system 1 are minimized.
[0045] The cooled urea-containing particles are then transported to a screening device 9, which separates undersized particles from the final product particles. The cooled undersized particles can also be returned to the fluidized bed granulator 3 via an air conveyor 19. The final product particles are transported to appropriate equipment not shown here for further processing. Thus, a suitable fine-mesh screen positioned downstream of the bulk flow cooler 4 operates within a temperature range of 30-50°C and is therefore optimally protected from urea abrasion or clogging, as the urea-containing particles have already cooled and hardened.
[0046] Figure 3 shows a further exemplary embodiment of the fluidized bed granulator system 1. In contrast to Figure 2, the exemplary embodiment according to Figure 3 provides only a single-stage preliminary screening. The crude material is screened in a screening device 9 and returned to the recirculation cooler only after cooling in a bulk flow cooler. In this exemplary embodiment, the screening device 9 comprises two screens. [Explanation of Symbols]
[0047] 1. Fluidized Bed Granulator System 2 Cooling Zones 3. Fluidized bed granulator 4. Bulk flow cooler 5. Roller shredder 6 Bucket conveyor 7. Preliminary screening device 8 Cooling device 9. Screening device 10 Collection containers 11. First Screen 12. Second Screen 13 Output of final product particles 14. Output of oversized particles 15 Output of undersized particles 16 Return entrance 17 Cooler 18 Recirculating cooler 19. Air conveyor 20 Dust Removal Units
Claims
1. A method for energy-optimized granulation of urea-containing particles in a fluidized bed granulator system (1), After granulation, the urea-containing particles are cooled to a temperature in the range of 80°C to 108°C in the cooling zone (2) of the fluidized bed granulator (3). After preliminary screening, at least a portion of the urea-containing particles are cooled to a temperature in the range of 30°C to 50°C by the bulk flow cooler (4). A method characterized by the following.
2. The method according to claim 1, characterized in that a two-stage preliminary screening is provided, in which urea-containing particles having a particle size greater than 10 mm are first separated, and then urea-containing particles having a particle size greater than 4 mm are separated.
3. The method according to claim 2, characterized in that, after the separation, the urea-containing particles having a particle size greater than 4 mm and less than 10 mm are cooled and pulverized, and the cooled and pulverized urea-containing particles are then entered into the fluidized bed granulator (3).
4. The method according to claim 3, characterized in that, after pulverization, the urea-containing particles having a particle size of more than 4 mm and less than 10 mm are entered into the fluidized bed granulator (3) by air transport.
5. The method according to claim 3 or 4, characterized in that the separated particles are cooled to about 65°C.
6. The method according to any one of claims 3 to 5, characterized in that the separated particles are crushed by a roller crusher (5).
7. The method according to any one of claims 1 to 6, characterized in that, after preliminary screening, the urea-containing particles having a particle size of less than 4 mm are subjected to dust removal.
8. The method according to any one of claims 1 to 7, characterized in that the urea-containing particles having a particle size of less than 4 mm are transported to the bulk flow cooler by a bucket conveyor (6).
9. The method according to any one of claims 1 to 8, characterized in that the urea-containing particles are cooled to a temperature in the range of 30°C to 50°C, and then urea-containing particles having a particle size of less than 2 mm are separated.
10. The method according to claim 9, characterized in that the separated particles having a particle size of less than 2 mm enter the fluidized bed granulator (3).
11. The method according to claim 9, characterized in that the separated particles having a particle size of less than 2 mm are entered into the fluidized bed granulator (3) by air transport.
12. A fluidized bed granulator system (1) for energy-optimized granulation of urea-containing particles, comprising the following elements operably connected to one another, a) A fluidized bed granulator (3) for granulating urea-containing particles, b) A cooling zone (2) located within the fluidized bed granulator (3) for cooling urea-containing particles to a temperature in the range of 80°C to 108°C using air, c) A preliminary screening device (7) for separating excessively large urea-containing particles, preferably having a particle size greater than 4 mm, after granulation. d) A cooling device (8) for cooling the urea-containing particles to a temperature in the range of 30°C to 50°C, comprising at least one bulk flow cooler (4), e) A screening device (9) for separating excessively small urea-containing particles having a particle size of less than 2 mm, and A fluidized bed granulator system (1) is provided with the following:
13. The fluidized bed granulator system (1) according to claim 12, characterized in that the preliminary screening device (7) comprises at least two screens, the first screen (11) enabling the separation of urea-containing particles having a particle size greater than 10 mm, and the second screen (12) enabling the separation of urea-containing particles having a particle size less than 10 mm but greater than 4 mm.
14. A fluidized bed granulator system (1) according to claim 12 or 13, characterized in that an air conveyor (19) is provided, which enables the transport of separated urea-containing particles having a particle size of less than 10 mm and greater than 4 mm to the fluidized bed granulator (3), and / or the air conveyor (12) enables the transport of separated urea-containing particles having a particle size of less than 2 mm to the fluidized bed granulator (3).
15. A fluidized bed granulator system (1) according to any one of claims 12 to 14, characterized in that it is designed and configured to carry out the method described in any one of claims 1 to 11.