LU103096B1 - Process for energy-optimized granulation of urea-containing particles and fluid bed granulator system - Google Patents

Abstract

Method for energy-optimized granulation of urea-containing particles and fluid bed granulator system The invention relates to a method for energy-optimized granulation of urea-containing particles in a fluid bed granulator system (1). In a method in which the energy required to cool the urea-containing particles is minimized, wherein the method and operation of the fluid bed granulator system (1) are optimized in terms of process technology, it is provided that the urea-containing particles are cooled after granulation in a cooling zone (2) of a fluid bed granulator (3) to a temperature in a range between 80 °C and 108 °C and that at least some of the urea-containing particles are cooled to a temperature in a range between 30 °C and 50 °C after pre-sieving by means of a bulk flow cooler (4).

Description

210617P00LU

LU103096

Description

Process for energy-optimized granulation of urea-containing particles and

fluid bed granulator system

The invention relates to a process for energy-optimized granulation of urea-containing

particles, in a fluid bed granulator system.

In addition, the invention relates to a fluid bed granulator system for energy-optimized

Granulation of urea-containing particles.

Due to the continuous growth of the world population, there is a constant need for reliable, easy to produce and inexpensive fertilizers. These conventional

Fertilizers can contain nitrogen, phosphate, sulfur, calcium, selenium, potassium or

Micronutrients. A common, widely used fertilizer contains urea as

Main component. The water-soluble urea is quickly broken down in the soil,

Ammonia and nitrate compounds are formed. Depending on the application, the fertilizer can only

Urea or a combination of urea with one or more of the above

components such as phosphate, sulfur, potassium or trace nutrients.

Urea can be produced on a large industrial scale by reacting ammonia with

Carbon dioxide can be produced in a (simplified) two-step reaction: 2 NH; + CO, 2 H,N-COONH, (1)

H2N-COONH4, 2 (NH2)aCO + H,O (2)

After synthesis, further process steps are required to obtain a transportable and storable urea fertilizer. Common technical processes include various granulation techniques such as prilling, drum granulation or

Fluid bed granulation. Prilling processes in particular have some critical disadvantages, such as relatively soft particles and sometimes deformed, inhomogeneous particles.

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These problems can be avoided by using a fluid bed granulation process, which results in harder, more stable and more homogeneous granules. The resulting granulated urea is particularly suitable for bulk blending.

In addition, there is less segregation or mechanical damage when mixing and transporting the urea-containing fertilizer. Size, size distribution,

Geometry and mechanical properties of the final product depend to a large extent on the

Temperature during the granulation process. Therefore, a controlled

Temperature environment is essential to obtain a reproducible product granulate with constant product properties, e.g. in terms of hardness, caking or

dust formation.

Fluid bed granulator systems are largely based on the use of ambient air for

Therefore, the capacity of a fluid bed granulator may be limited depending on the temperature of the ambient air or the amount of heat generated by the

This can lead to high temperatures in the plant, which reduces the amount of product that can be produced or leads to a reduction in the

product quality and a deterioration of the operating conditions. In addition, under certain operating conditions (e.g. very high product load) the

Granulation temperature can become too high. This is especially the case when the plant is operating at high capacity or high ambient temperature or both. In addition, many plants are already equipped with a fluid bed cooler to reduce the granule temperature from around 95 °C to 60-70 °C. This requires a large amount of ambient air and can be difficult even under the above operating conditions.

Cooling the urea-containing particles requires a lot of energy to provide the cooling air. In addition, it is important to cool the urea-containing particles at times that are favorable for the process in order to make the process as efficient as possible.

The invention is therefore based on the object of providing a method for energy-optimized

Granulation of urea-containing particles and a fluid bed granulator system in which the energy required for cooling the urea-containing particles is minimized, whereby the process and operation of the fluid bed granulator system are optimized in terms of process technology.

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This object is achieved in the present invention by the features of the characterizing part of claim 1 in that the urea-containing particles after the

Granulation in a cooling zone of a fluid bed granulator to a temperature in a range between 80 °C and 108 °C, and that at least some of the urea-containing particles are, after pre-sieving, in a second step by means of a bulk flow

cooler to a temperature in a range between 30 °C and 50 °C.

The cooling zone can be a fluid bed cooler, which can achieve air cooling of the urea-containing particles by means of a fan. In order to save investment costs, the fluid bed cooler is arranged in the fluid bed granulator. Since the energy required for compressing the cooling air is comparatively high, the invention provides that the urea-containing particles are cooled in the cooling zone to a temperature between 80 °C and 108 °C. The urea-containing particles leave the fluid bed granulator or a granulation zone within the fluid bed granulator with a

Temperature above 100 °C. The cooling capacity in the cooling zone is therefore energetically low compared to the cooling in the second step.

A bulk flow cooler is a heat exchanger in which the material to be cooled

Product can flow relatively gently between welded heat exchanger plates according to the “first in, first out” principle. Cooling water flows at a suitable temperature on the other side of the plates. This indirect method of heat transfer reduces the

The need for fans, bag filters or washers is minimized. This provides a cost-effective solution for cooling, but also for heating bulk materials. In addition, the cooling process itself is emission-free.

With the help of the bulk flow cooler, the urea-containing particles or a part of the urea-containing particles, i.e. the part that still enters the bulk flow after pre-screening,

cooler, cooled to a temperature between 30 °C and 50 °C. The bulk flow

The cooler therefore takes over the majority of the cooling capacity, whereas the

The cooling capacity of the cooling zone in the fluid bed granulator is low relative to the cooling capacity of the bulk flow cooler. Cooling using a bulk flow cooler with appropriate cooling water is more energy efficient than cooling in the fluid bed using compressed air, which minimizes the overall energy requirement of the fluid bed granulator system.

Cooling water is usually sufficient, especially in urea plants, in a suitable

Temperature level (flow/return, for example 30/40 °C) available and specifically clearly

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LU103096 cheaper than the electrical energy that would otherwise be needed to compress the cooling air.

Further preferred embodiments of the invention will become apparent from the remaining details given in the

features mentioned in the subclaims.

In a first embodiment of the invention, a two-stage pre-screening is provided, whereby firstly urea-containing particles with a grain size > 10 mm are separated and then urea-containing particles with a grain size > 4 mm. The product leaves the

Fluid bed granulator with a relatively wide grain size range of approx. 0.5 to 10 mm and above. Therefore, it can be advantageous to provide a two-stage pre-screening, in which the larger particles are separated first, followed by the so-called

Coarse material, i.e. particles with a grain size > 4 mm but < 10 mm, are separated.

In addition, in a further embodiment of the method according to the invention, it can be provided that the urea-containing particles with a grain size > 4 mm and < 10 mm are cooled and crushed after separation and that the cooled and crushed urea-containing particles are subsequently fed into the fluid bed granulator.

The coarser fraction, i.e. the coarse material, accounts for only a small proportion of the

Product is present. The requirements for the sieve used to separate the

The amount of coarse material, i.e. urea-containing particles > 4 mm and < 10 mm, is comparatively low, since the majority of the particles with a smaller grain size fall through. The

The amount of urea abrasion or clogging during operation is therefore low.

After crushing, the urea-containing particles can be separated, for example by means of a

bucket elevator, into the fluidized bed granulator so that the crushed urea-containing particles can be further granulated.

In a particularly advantageous embodiment of the method according to the invention, the urea-containing particles with a grain size > 4 mm and < 10 mm are fed into the fluid bed granulator by means of pneumatic conveying. The advantage of pneumatic conveying or a pneumatic conveying system for conveying the particles back into the fluid bed granulator is that no bucket elevator — which is common in the state of the art — is required. In this way, the building height can be kept low and only needs to correspond to the height of the bulk flow cooler. The conveying air flow is

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LU103096 For dense phase conveying, a pressure of approx. 1 to 2 bar and approx. 100 °C in a quantity of only < 1% of the fluidization air of the fluid bed granulator is required.

In order to simplify further processing of the urea-containing particles with a grain size of > 4 mm and < 10 mm, a further embodiment of the inventive

The process involves cooling the separated particles to approximately 65 °C.

During further processing or comminution of the coarse material, it is advantageous that the particles are cooled beforehand in order to avoid urea abrasion and clogging.

For this purpose, in a further advantageous embodiment of the invention, it can be provided that the separated particles are crushed by means of a roller crusher.

For roller crushers, a temperature of 65 °C for the urea-containing particles is optimal.

Optionally, in a further embodiment of the method according to the invention, it can be provided that after the pre-screening, a dedusting of the urea-containing particles with a grain size of < 4 mm is carried out. The dedusting can be carried out according to any adequate

Methods known from the state of the art are carried out.

A practical variant of the conveyance of the particles is a further design of the

The procedure provides that the urea-containing particles with a grain size of < 4 mm are separated by means of a

The bucket elevator can be used to transport the urea-containing particles < 4 mm into the bulk flow cooler. After pre-screening, both the on-size product (2 to 4 mm) and the fines (< 2 mm) that still need to be separated are present. The bucket elevator can transport the urea-containing particles into the bulk flow cooler, through which they pass from top to bottom with the help of gravity. This bucket elevator does not have to be as high as is usual in classic, state-of-the-art concepts, because the

Screening and recirculation of the fines can be arranged at a lower level in the building of the fluid bed granulation system. In this way, the

Construction costs for the steel structure of the building are minimized.

In order to achieve a desired grain size, a further embodiment of the method according to the invention provides that after cooling the urea-containing

Particles to a temperature in a range between 30 °C and 50 °C urea-containing

Particles with a grain size of < 2 mm are separated. A corresponding fine sieve, which is arranged behind the bulk flow cooler, then works accordingly in

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LU103096 a temperature range of 30 to 50 °C and is therefore optimally protected against urea abrasion or clogging because the urea-containing particles are already cooled and hardened.

In a particularly advantageous embodiment of the method according to the invention, it is provided that the separated particles with a grain size < 2 mm are fed into the

The discharge of the fine material is below the level of the

Fluid bed granulator. One possibility for conveying the fine material is therefore the

Use of a bucket elevator.

In a further preferred embodiment of the invention, it can be provided that the separated particles with a grain size of < 2 mm are conveyed by pneumatic conveyance into the

Fluid bed granulator. Analogous to the coarse material, a pneumatic conveyor or a pneumatic conveyor system for conveying the particles back into the

The advantage of the fluid bed granulator is that no bucket elevator, as is usual in the state of the art, is required. This means that the building height can be kept low and only needs to correspond to the height of the bulk flow cooler.

For dense phase conveying, a pressure of approx. 1 to 2 bar and approx. 100 °C in a quantity of only < 1% of the fluidization air of the fluid bed granulator is required as the conveying air flow. In addition, the energy balance of the fluid bed granulator can be positively influenced because the cooled fine material, i.e. the urea-containing particles < 2 mm, can be fed into different chambers of the fluid bed granulator at a temperature of just over 45 °C.

The above object is also achieved by a fluid bed granulator system for energy-optimized granulation of urea-containing particles comprising the

elements in active connection: a) a fluid bed granulator for granulating urea-containing particles, b) a cooling zone arranged in the fluid bed granulator for cooling urea-containing particles with air to a temperature in a range between 80 °C and 108 °C,

C) a pre-screening device for separating urea-containing particles which are too large after granulation, preferably with a grain size > 4 mm, d) a cooling device for cooling the urea-containing particles to a temperature in a range between 30 °C and 50 °C, wherein the cooling device comprises at least one bulk flow

cooler includes,

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LU103096 e) a screening device for separating urea-containing particles which are too small, preferably with a grain size of < 2 mm.

In a first embodiment of the fluid bed granulator system according to the invention, it is provided that the pre-screening device has at least two screens, wherein urea-containing particles with a grain size > 10 mm can be separated with a first screen and wherein urea-containing particles with a grain size > 10 mm and < 4 mm can be separated with a second screen.

In a further advantageous embodiment of the inventive

A pneumatic conveying device is provided in the fluid bed granulator system, whereby separated urea-containing particles with a grain size > 10 mm and < 4 mm can be conveyed into the fluid bed granulator by means of the pneumatic conveying device and/or whereby separated urea-containing particles with a grain size < 2 mm can be conveyed into the fluid bed granulator by means of the pneumatic conveying device.

In a further embodiment of the fluid bed granulator system according to the invention, it is provided that the fluid bed granulator system is designed and set up to carry out a method according to the invention. The above statements regarding the method according to the invention also apply accordingly to the inventive

fluid bed granulator system.

The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless stated otherwise in individual cases.

The invention is described below in exemplary embodiments based on the associated

Drawings explain:

Figure 1 is a schematic representation of an investment cost-optimized

state-of-the-art fluid bed granulator system,

Figure 2 is a schematic representation of a fluid bed granulator system according to a

Embodiment of a fluid bed granulator system according to the invention and

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Figure 3 shows a schematic design of a fluid bed granulator system according to a particularly preferred embodiment.

Figure 1 shows an exemplary schematic representation of a fluid bed granulator system 1 according to the prior art. The fluid bed granulation system 1 comprises a

Fluid bed granulator 3 and a cooling zone 2 arranged in the fluid bed granulator 3 or connected to the fluid bed granulator 3. The term "connected" in the sense of

The invention generally relates to connecting means capable of

To transport or transfer process liquids, solids or gases and/or mixtures thereof, e.g. pipes, ducts, pumps, hoses and also includes tanks, containers and/or pumps. This definition includes connection devices that are suitable for gaseous, solid and liquid media at low pressure (below 1 bar) and for gaseous, solid and liquid media at high pressure (over 1 bar, preferably up to 10 bar).

In the cooling zone, the particles are cooled to a temperature range < 70 °C and then fed into a screening device 9, which is connected to the cooling zone 2. The

Sieving device 9 separates the granular particles from the fluid bed granulator 3 into size-appropriate

Product particles within the desired product size and into oversized (above the desired product size) particles and undersized (below the desired

Product size) particles. In addition, a pre-screening device 7 is provided to remove particles whose

Grain size is much larger than the grain size of the oversized particles. These "lumps" are removed from the process and fed into a collecting container 10. The other urea-containing particles are fed into the screening device 9 by means of a bucket elevator 6.

The structure of the sieve device 9 comprises a first sieve 11 with a mesh size above the desired particle size and a second sieve 12 below the desired

particle size, whereby the screening device 9 is divided into three parts. The screening device 9 also comprises an outlet for the final product particles 13 between the first

sieve 11 and the second sieve 12, an outlet for oversized particles 14, e.g. above the first sieve 11, and an outlet for undersized particles 15 below the second sieve 12.

The outlet for the undersized particles 15 is connected to the fluid bed granulator 1 via a first recirculation inlet 16, and the outlet for the oversized particles 14 is connected to the fluid bed granulator 1 via a roll crusher 5 or similar device, thereby producing crushed particles.

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The final product particles are passed from the screening device 9 into a cooler 17 for final hardening and cooling. The final product (not shown here) can then be packaged or otherwise processed.

Figure 2 shows a schematic representation of a fluid bed granulator system 1 according to a

Embodiment of a fluidized bed granulator system according to the invention 1. In the

Compared to the prior art, the cooling zone 2 within the fluidized bed granulator 3 is kept as small as possible so that the urea-containing particles leave the fluidized bed granulator 3 or the cooling zone 2 with a temperature in a range between 80 °C and 108 °C. Furthermore, a pre-screening device 7 is provided in order to remove particles whose

Grain size is far above the grain size of the oversized particles. These "lumps" are removed from the process and fed into a collecting container 10. The other urea-containing particles are fed into the screening device 9 by means of a bucket elevator 6. The pre-screening device 7 also includes a first screen 11, which separates the oversized particles from the product particles and the undersized particles.

It is intended that the oversized particles, which are produced in a small amount compared to the remaining urea-containing particles, are subsequently

return cooler 18 before they are crushed in a roller crusher 5 and returned to the fluid bed granulator 3 by means of a pneumatic conveyor device 19. During further processing or crushing of the coarse material, it is advantageous for the particles to be cooled beforehand in order to avoid urea abrasion and clogging.

In addition, in this embodiment, a dedusting unit 20 is provided, by means of which the flow of undersized particles and product particles can be dedusted after pre-screening.

The undersized particles and the product particles are fed into a cooling device 8 after the pre-screening device 7, wherein the cooling device 8 comprises a bulk flow cooler 4. In the bulk flow cooler 4, the undersized particles and the product particles are cooled to a

Temperature in a range between 30 and 50 °C. The pneumatic

Conveyor device 19 for conveying the particles back into the fluid bed granulator 3, has the

The advantage is that no bucket elevator, as is usual in the state of the art, is required. In this way, the building height can be kept low and only needs to be adapted to the height of the bulk flow

cooler 4.

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With the help of the Bulkflow Cooler 4, the urea-containing particles or a part of the urea-containing particles, i.e. the part that still enters the bulk flow after the pre-screening

Cooler 4 is cooled to a temperature between 30 °C and 50 °C. The bulk flow

Cooler 4 therefore takes over the majority of the cooling capacity, whereas the required

Cooling capacity of cooling zone 2 is low relative to the cooling capacity of bulk flow cooler 4. The

Cooling by means of bulk flow cooler 4 with appropriate cooling water is more energy efficient than cooling in the fluidized bed using compressed air, which reduces the overall energy requirement of the

fluid bed granulator system 1 is minimized.

The cooled urea-containing particles are then conveyed to a screening device 9, in which the undersized particles are separated from the final product particles. The undersized cooled particles can be removed via the pneumatic

The final product particles are conveyed to the fluid bed granulator 3 via the conveyor device 19. The final product particles are conveyed to corresponding devices (not shown here) for further processing. A corresponding fine sieve, which is arranged behind the bulk flow cooler 4 in terms of flow, then works accordingly in a

Temperature range of 30 to 50 °C and is therefore optimally protected against urea abrasion or clogging because the urea-containing particles have already cooled and hardened.

Figure 3 shows another embodiment of a fluid bed granulator system 1. In

In contrast to Figure 2, in the embodiment according to Figure 3 only a single-stage

Pre-screening is provided. The coarse material is only cooled in the bulk flow cooler in the

Sieving device 9 and returned to the recirculation cooler. In this embodiment, the sieving device 9 comprises two sieves.

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List of reference symbols 1 Fluid bed granulator system 2 Cooling zone 3 Fluid bed granulator 4 Bulk flow cooler

Roller crusher 6 Bucket elevator 7 Pre-screening device 8 Cooling device 9 Screening device

Collection container 11 First sieve 12 Second sieve 13 Outlet for final product particles 14 Outlet for oversized particles

Outlet for undersized particles 16 Recirculation inlet 17 Cooler 18 Recirculation cooler 19 Pneumatic conveyor

dust extraction unit

Claims (15)

210617P00LU LU103096 patent claims 1. Process for energy-optimized granulation of urea-containing particles in a fluid bed granulator system (1), characterized in that the urea-containing particles are cooled after granulation in a cooling zone (2) of a fluid bed granulator (3) to a temperature in a range between 80 °C and 108 °C, and that at least some of the urea-containing particles are cooled to a temperature in a range between 30 °C and 50 °C after pre-sieving by means of a bulk flow cooler (4). 2. Method according to claim 1, characterized in that a two-stage pre-screening is provided, whereby firstly urea-containing particles with a grain size > 10 mm are separated and then urea-containing particles with a grain size > 4 mm. 3. Process according to claim 2, characterized in that the urea-containing particles with a grain size > 4 mm and < 10 mm are cooled and crushed after separation and that the cooled and crushed urea-containing particles are subsequently fed into the fluid bed granulator (3). 4. Process according to claim 3, characterized in that the urea-containing particles with a grain size > 4 mm and < 10 mm are fed into the fluid bed granulator (3) after comminution by means of pneumatic conveying. 5. Process according to claim 3 or 4, characterized in that the separated particles are cooled to about 65 °C. 6. Method according to one of claims 3 to 5, characterized in that the separated particles are crushed by means of a roller crusher (5). 210617P00LU -2- LU103096 7. Process according to one of claims 1 to 6, characterized in that after the pre-sieving, a dedusting of the urea-containing particles with a grain size <4 mm is carried out. 8. Method according to one of claims 1 to 7, characterized in that the urea-containing particles with a grain size < 4 mm are transported into the bulk flow cooler by means of a bucket elevator (6). 9. Method according to one of claims 1 to 8, characterized in that after cooling the urea-containing particles to a temperature in a range between °C and 50 °C, urea-containing particles with a grain size < 2 mm are separated. 10. Process according to claim 9, characterized in that the separated particles with a grain size < 2 mm are fed into the fluidized bed granulator (3). 11. Process according to claim 9, characterized in that the separated particles with a grain size < 2 mm are fed into the fluid bed granulator (3) by means of pneumatic conveying. 12. Fluid bed granulator system (1) for energy-optimized granulation of urea-containing particles, comprising the elements in operative connection with one another a) a fluid bed granulator (3) for granulating urea-containing particles, b) a cooling zone (2) arranged in the fluid bed granulator (3) for cooling urea-containing particles with air to a temperature in a range between 80 °C and 108 °C, c) a pre-screening device (7) for separating urea-containing particles that are too large after granulation, preferably with a grain size > 4 mm, d) a cooling device (8) for cooling the urea-containing particles to a temperature in a range between 30 °C and 50 °C, wherein the cooling device comprises at least one bulk flow cooler (4), e) a screening device (9) for separating urea-containing particles that are too small, preferably with a grain size < 2 mm. 210617P00LU -3- LU103096 13. Fluid bed granulator system (1) according to claim 12, characterized in that the pre-screening device (7) has at least two screens, wherein urea-containing particles with a grain size > 10 mm can be separated with a first screen (11) and wherein urea-containing particles with a grain size < 10 mm and > 4 mm can be separated with a second screen (12). 14. Fluid bed granulator system (1) according to claim 12 or 13, characterized in that a pneumatic conveying device (19) is provided, wherein separated urea-containing particles with a grain size of < 10 mm and > 4 mm can be conveyed into the fluid bed granulator (3) by means of the pneumatic conveying device (19) and/or wherein separated urea-containing particles with a grain size of < 2 mm can be conveyed into the fluid bed granulator (3) by means of the pneumatic conveying device (12). 15. Fluid bed granulator system (1) according to one of claims 12 to 14, characterized in that the fluid bed granulator system (1) is designed and configured to carry out a method according to one of claims 1 to 11.