INTERNAL COOLING SYSTEM FOR FLUID-BED GRANULATION PLANTS

Abstract

A fluid-bed granulator system with adjustable cooling includes a fluid-bed granulator. A first cooler is externally connected to the fluid-bed granulator or forms an internal part of the fluid-bed granulator. A product screen is connected to the first cooler and the fluid-bed granulator. The product screen includes an exit for final on-size product particles, an exit for oversized particles, and an exit for undersized particles. The exit for the undersized particles is connected to the fluid-bed granulator and the exit for the oversized particles is connected to the fluid-bed granulator via one or more crushers. A recycle cooler is located and connected between the fluid-bed granulator and the exit for undersized particles and/or the recycle cooler is located between the fluid-bed granulator and the exit for the oversized particles. The recycle cooler is connected to the fluid-bed granulator via one or more recycle inlets.

Claims

1.-15. (canceled)

16. Fluid-bed granulator system with adjustable cooling setup at least comprising: a fluid-bed granulator, a first cooler externally connected to the fluid-bed granulator or forming an internal part of the fluid-bed granulator, a product screen connected to the first cooler and the fluid-bed granulator, wherein the product screen comprises an exit for final on-size product particles, an exit for oversized particles, and an exit for undersized particles, wherein the exit for the undersized particles is connected to the fluid-bed granulator and wherein the exit for the oversized particles is connected to the fluid-bed granulator via one or more crushers, a recycle cooler located and connected between the fluid-bed granulator and the exit for undersized particles, and/or wherein the recycle cooler is located between the fluid-bed granulator and the exit for the oversized particles, and wherein the recycle cooler is connected to the fluid-bed granulator via one or more recycle inlets.

17. The fluid-bed granulator system of claim 16 wherein the fluid-bed granulator comprises a granulator space inside the fluid-bed granulator, a perforated plate located inside the granulator space, spray nozzles located in, on, above or beside the perforated plate, a fluidization air inlet, supply lines for atomization air connected to the spray nozzles, supply lines for a liquid melt connected to the spray nozzles, a granulation seeds inlet, a granulator outlet opening, and an air vent opening.

18. The fluid-bed granulator system of claim 16 wherein the first cooler comprises a cooler space inside the first cooler, a perforated plate located inside the cooler space, a product inlet, a fluidization air inlet, a cooler outlet opening, and an air vent opening.

19. The fluid-bed granulator of claim 16 wherein the recycle cooler uses a gas or a liquid as cooling medium.

20. The fluid-bed granulator system of claim 16 wherein the recycle cooler comprises a bulk flow cooler.

21. The fluid-bed granulator system of claim 16 wherein the perforated plate comprises, in the direction of flow: a growing zone and a cooling zone.

22. The fluid-bed granulator system of claim 21 wherein the recycle cooler is/are connected to the growing zone and/or the cooling zone via the recycle inlets.

23. The fluid-bed granulator system of claim 21 wherein the growing zone and the cooling zone are divided by partition walls.

24. The fluid-bed granulator system of claim 21 wherein the growing zone is connected to the recycle cooler via the recycle inlets.

25. A method for a temperature controlled granulation of urea containing particles at least comprising the following steps: introducing seed granules into a fluid-bed granulator; granulating the seed granules and receiving product granules; conveying the product granules to a first cooler and receiving pre-cooled product granules; conveying the pre-cooled product granules into a product screen and receiving final on-size product particles, oversized particles, and undersized particles; conveying the undersized particles into the fluid-bed granulator, removing the final on-size product particles from the process and conveying the oversized particles into a crusher and receiving crushed particles; conveying the crushed particles into the fluid-bed granulator; wherein the oversize and/or the undersized particles are transferred into a recycle cooler before entering the fluid-bed granulator.

26. The method of claim 25 wherein the temperature of the granulation step is kept in a range of between 102 C. and 112 C.

27. The method of claim 25 wherein the perforated plate comprises, in the direction of flow, a growing zone and a cooling zone

28. The method of claim 27 wherein the undersized particles and/or the crushed particles are conveyed in the first growing zone and/or the first cooling zone.

29. A urea granulation plant comprising a fluid-bed granulator system comprising: a fluid-bed granulator, a first cooler externally connected to the fluid-bed granulator or forming an internal part of the fluid-bed granulator, a product screen connected to the first cooler and the fluid-bed granulator, wherein the product screen comprises an exit for final on-size product particles, an exit for oversized particles, and an exit for undersized particles, wherein the exit for the undersized particles is connected to the fluid-bed granulator and wherein the exit for the oversized particles is connected to the fluid-bed granulator via one or more crushers; wherein a recycle cooler is located and connected between the fluid-bed granulator and the exit for undersized particles, and/or wherein the recycle cooler is located between the fluid-bed granulator and the exit for the oversized particles, and wherein the recycle cooler is connected to the fluid-bed granulator via one or more recycle inlets.

Description

[0056] The invention is further described in the following figures. The figures are meant for illustrative purpose only and do not restrict the scope of protection. The figures are not true to scale.

[0057] FIG. 1 shows an exemplary schematic view of a fluid-bed granulator system according to the state of the art,

[0058] FIG. 2 shows a schematic view of a fluid-bed granulator system according to the invention,

[0059] FIG. 3 shows a schematic view of a fluid-bed granulator according to the invention and

[0060] FIG. 1 shows an exemplary schematic view of a fluid-bed granulator system according to the state of the art. The Fluid-bed granulator system comprises a fluid-bed granulator (1) and a first cooler (2) connected with the fluid-bed granulator (1). The term connected within the meaning of the invention generally refers to connection means which are able/suitable to transport or transfer process liquids, solids or gases and/or mixtures thereof, e.g. pipes, ducts, pumps, hoses and further includes tanks, reservoirs and/or pumps. This definition includes connection means suitable for low pressure gaseous, solids and liquid mediums (below 1 bar) and high pressure (above 1 bar, preferably above 10 bar) gaseous, solid and liquid mediums. A product screen (3) is connected with the first cooler (2). The product screen (3) (or sieve) separates the granular particles from the product cooler into on-size product particles (3a) within the desired product size and into oversized (above the desired product size) particles (3b) and undersized (below the desired product size) particles (3c). The minimum screen (3) setup would include a first screen with a mesh size above the desired particle size and a second screen below the desired particle size, thus dividing the product screen into three parts. The product screen further comprises an exit for final on-size product particles (3a), between the first screen and second screen, an exit for oversized particles (3b), e.g. above the first screen, and an exit for undersized particles (3c), below the second screen. The exit for the undersized particles (3a) is connected (via the recycle inlet (16)) with the fluid-bed granulator (1) and the exit for oversized particles (3b) is connected with the granulator (1) via a crusher (4) or a similar device, resulting in crushed particles (3d). The final on-size product particles (3a) are transferred to suitable further processing units (22) like scales and packaging devices.

[0061] FIG. 2 shows a schematic view of a fluid-bed granulator system according to the invention. The principle setup is identical with the setup described in FIG. 1. According to the present invention, a recycle cooler (6) is located between the exit for undersized particles (3c) and the fluid-bed granulator (1), thereby effectively cooling the undersized particles (3c) before entering the fluid-bed granulator (1) as new seed particles. This recycle cooler (6) effectively reduces the temperature of the respective granular particles, preferably by conveying undersized particles (3c) to the fluid-bed granulator with a temperature between 45 C. to 80 C. The undersized particles (3c) thereby effectively cool the fluid-bed granulator without significantly altering the process performance. The undersized particles enter and are distributed in the fluid-bed granulator on one or more different spots via the recycle inlets (16), e.g. the first growing zone (7a1) and the second growing zone (7a2).

[0062] FIG. 3 shows a schematic view of a fluid-bed granulator according to the invention. FIG. 3 shows the schematic view of the fluid-bed granulator system according to the invention comprising a fluid bed granulator (1) with a granulator space (1a) inside the fluid-bed granulator (1). A perforated plate (7) is located inside the granulator space (1a). Spray nozzles (8) are located on or above the perforated plate (7), a fluidization air inlet (9) is located below the perforated plate (2). Multiple supply lines for atomization air (10) and supply lines for a liquid melt (11) are connected to the spray nozzles (8). Optionally, these supply lines (10, 11) can be combined in one line. The fluid-bed granulator (1) further comprises a granulation seeds inlet (12), preferably in connection with a not shown product sieve or crusher, a granulator outlet opening (13) and an air vent opening (14). The fluid-bed (21) is formed by the corresponding granular particles (20) utilizing the fluidization air from below the perforated plate (7). The fluidization air flow is indicated by arrows labeled (II), the flow direction of the fluid bed granular particles (20) is indicated by arrows labeled (I). The fluid-bed (21) is preferably divided by one or more partition plates (15), separating a shown growing zone (7a) and cooling zone (7b).

REFERENCE SIGNS

[0063] (1) fluid-bed granulator [0064] (1a) granulator space [0065] (2) first cooler [0066] (3) product screen [0067] (3a) final product on-size particles [0068] (3b) oversized particles [0069] (3c) undersized particles [0070] (3d) crushed particles [0071] (4) crusher [0072] (6) recycle cooler [0073] (7) perforated plate [0074] (7a) growing zone (first 7a1, second 7a2 respectively, 7a.sub.i accordingly i=3, 4, 5, 6, . . . ) [0075] (7b) cooling zone (first 7b1, second 7b2 respectively, 7b.sub.i accordingly i=3, 4, 5, 6, . . . ) [0076] (8) spray nozzles [0077] (9) fluidization air inlet [0078] (10) supply lines for atomization air [0079] (11) supply lines for a liquid melt [0080] (12) granulation seeds inlet [0081] (13) granulator outlet opening [0082] (14) air vent opening [0083] (15) partition plates [0084] (16) recycle inlet [0085] (20) granular particles [0086] (21) fluid-bed [0087] (22) processing units