FLUID BED GRANULATOR

Abstract

A fluidized bed granulator for production of urea-containing or nitrate-containing granules may include a granulator interior having granulator interior walls with a first granulator side wall, a second granulator side wall, a granulator front wall that extends transversely to the granulator side walls, and a granulator back wall that likewise extends transversely at the opposite end of the granulator interior from the granulator front wall, a horizontal perforated plate that bounds the granulator interior in a downward direction, a seed entry opening, and a granule exit opening that is disposed at a distance in front of the granulator back wall. A process for producing urea-containing or nitrate-containing granules may utilize the fluidized bed granulator.

Claims

1.-28. (canceled)

29. A fluidized bed granulator for production of granules that contain urea or nitrate, the fluidized bed granulator comprising: a granulator interior having granulator interior walls that include a first granulator side wall, a second granulator side wall, a granulator front wall that extends transversely to the granulator side walls, and a granulator back wall that extends transversely at an opposite end of the granulator interior from the granulator front wall; a horizontal perforated plate that bounds the granulator interior in a downward direction; a seed entry opening; and a granule exit opening disposed at a distance in front of the granulator back wall.

30. The fluidized bed granulator of claim 29 wherein the granule exit opening is disposed within the horizontal perforated plate.

31. The fluidized bed granulator of claim 29 comprising a deflection device in the granulator interior configured to cause a deflection of a flow of granule particles in the granulator interior such that the granule particles are deflected at least once in a direction other than an initial flow direction toward the granule exit opening.

32. The fluidized bed granulator of claim 31 wherein the deflection device is configured to cause multiple deflections of the flow of the granule particles in the granulator interior that are different than the initial flow direction toward the granule exit opening.

33. The fluidized bed granulator of claim 31 wherein the deflection of the flow of the granule particles in the granulator interior is by 180° relative to the initial flow direction.

34. The fluidized bed granulator of claim 31 wherein the deflection device comprises a deflection plate that extends generally in the initial flow direction of the granule particles or at an acute angle to the initial flow direction and is disposed at a distance from the granulator side walls.

35. The fluidized bed granulator of claim 31 wherein the deflection device comprises deflection plates that form an acute angle with one another, that form a right angle with one another, or that are arranged parallel to one another.

36. The fluidized bed granulator of claim 31 wherein the deflection device comprises: a first deflection plate that extends generally in the initial flow direction of the granule particles; and a second deflection plate that extends in front of the granule exit opening transverse to the initial flow direction of the granule particles.

37. The fluidized bed granulator of claim 31 wherein the granule exit opening is surrounded on two or three sides by deflection plates, by no deflection plate, or by a deflection plate with an opening disposed opposite the granulator back wall.

38. The fluidized bed granulator of claim 29 comprising at least one of: a second seed entry opening disposed in the granulator front wall; seed entry openings in the first granulator side wall; or seed entry openings in the second granulator side wall.

39. The fluidized bed granulator of claim 38 wherein the second seed entry opening, the seed entry openings in the first granulator side wall, and/or the seed entry opening in the second granulator side wall are disposed in conjunction with a growth zone.

40. The fluidized bed granulator of claim 29 wherein the granule exit opening is disposed within the horizontal perforated plate and is spaced apart from and does not touch the granulator back wall.

41. The fluidized bed granulator of claim 29 comprising deflection plates in the granulator interior configured to cause a deflection of a flow of granule particles in the granulator interior such that the granule particles are deflected at least once in a direction other than an initial flow direction toward the granule exit opening, wherein the deflection plates are arranged in a U-shape or such that the deflection plates ensheath the granule exit opening.

42. The fluidized bed granulator of claim 29 wherein above the horizontal perforated plate the granulator interior is divided into growth zones and cooling zones, as viewed in a flow direction.

43. The fluidized bed granulator of claim 42 comprising dividing walls disposed between the growth zones and the cooling zones, wherein the dividing walls have passage openings.

44. The fluidized bed granulator of claim 42 wherein the granule exit opening is disposed within a cooling zone.

45. The fluidized bed granulator of claim 34 wherein the deflection plate is configured as a portion of a dividing wall.

46. The fluidized bed granulator of claim 29 wherein the granule exit opening is connected via a coarse screen to a conveying device.

47. The fluidized bed granulator of claim 46 wherein the conveying device is connected to a downstream screen apparatus.

48. The fluidized bed granulator of claim 46 wherein in a flow direction of granule particles the conveying device is disposed at a distance of 20% to 80% of a total length of the first granulator side wall or of the second granulator side wall.

49. The fluidized bed granulator of claim 29 wherein the granule exit opening is connected first to a coarse screen followed by a separate fluidized bed cooler.

50. The fluidized bed granulator of claim 29 wherein the horizontal perforated plate has inclined openings at an angle of 20° to 60° relative to a surface of the perforated plate.

51. The fluidized bed granulator of claim 50 wherein the inclined openings are inclined in different directions.

52. The fluidized bed granulator of claim 29 wherein one or both of the granulator side walls is arranged vertically.

53. The fluidized bed granulator of claim 29 wherein one or both of the granulator side walls, as viewed in a vertical direction, is in an inclined arrangement from a center line of the fluidized bed granulator outward.

54. A process for producing a granular material containing urea or nitrate, the process comprising: providing a urea-containing and/or nitrate-containing melt; spraying the urea-containing and/or nitrate-containing melt into a fluidized bed granulator that comprises: a granulator interior having granulator interior walls that include a first granulator side wall, a second granulator side wall, a granulator front wall that extends transversely to the granulator side walls, and a granulator back wall that extends transversely at an opposite end of the granulator interior from the granulator front wall, a horizontal perforated plate that bounds the granulator interior in a downward direction, a seed entry opening, and a granule exit opening disposed at a distance in front of the granulator back wall; and granulating the urea-containing and/or nitrate-containing melt and obtaining a urea-containing and/or nitrate-containing granular material.

55. The process of claim 54 wherein the urea-containing and/or nitrate-containing melt comprises a substance selected from a group consisting of ammonium sulfate, elemental sulfur, ammonium nitrate, trace elements, granulation additives, emulsification additives, or mixtures thereof.

Description

[0049] The figures show:

[0050] FIG. 1: a schematic top view of a fluidized bed granulator according to the prior art;

[0051] FIG. 2: a schematic top view of an illustrative fluidized bed granulator of the invention;

[0052] FIG. 3: a further schematic top view of the fluidized bed granulator of the invention;

[0053] FIG. 4: a further schematic top view of an alternative configuration of the fluidized bed granulator of the invention;

[0054] FIG. 5: a further preferred schematic top view of the fluidized bed granulator of the invention;

[0055] FIG. 6: a schematically simplified side view of a fluidized bed granulator according to the prior art;

[0056] FIG. 7: a corresponding schematically simplified side view of a fluidized bed granulator of the invention.

[0057] FIG. 1 shows a schematic top view of a conventional fluidized bed granulator according to the prior art, comprising at least one granulator interior 1 with granulator interior walls 1a bounding said granulator interior. The granulator interior walls 1a comprise at least one first, roughly vertical granulator side wall 1a.1 which is preferably inclined outward slightly away from the center line of the fluidized bed granulator in the upward direction, which bounds the granulator interior along a first longitudinal side, a second, roughly vertical granulator side wall 1a.2 which is preferably inclined outward slightly away from the center line of the fluidized bed granulator in the upward direction, which runs parallel and at a distance from the first granulator side wall and bounds the granulator interior along its second longitudinal side, a preferably roughly vertical granulator front wall 1a.3 that preferably runs in transverse direction to the two granulator side walls and connects these to one another, and a preferably roughly vertical granulator back wall 1a.4 that runs at a distance from and preferably parallel to the granulator front wall and hence is opposite the granulator front wall. Thus, the fluidized bed granulator shown in the working example has a granulator interior of preferably rectangular outline, which could possibly even be square. By way of simplification, in the present application, the term “longitudinal side” is used, which corresponds to the extension of the fluidized bed granulator in conveying direction of the granule particles in the granulator interior as indicated by the arrow in FIGS. 1 and 2. The granulator front wall 1a.3 which is on the side on which the granule particles that do not meet the specification enter the granulator interior, and the granulator back wall 1a.4 which is on the side on which the granule particles exit from the granulator interior in a conventional fluidized bed granulator, thus run in transverse direction and transverse to the main conveying direction of the granule particles.

[0058] The granulator interior 1 in which the fluidized bed is produced from the granule particles is bounded at the bottom by a perforated plate 2 which generally runs horizontally and which, according to the representation, may for example (but not exclusively) extend over the entire length and over the entire width of the granulator interior 1. Thus, above this perforated plate 2, in a roughly cuboidal or trough-shaped volume, a fluidized bed of granule particles is generated. In, above or on the perforated plate are mounted multiple spray nozzles 5 that are generally in a spaced-apart arrangement from one another, which may be arranged in rows, for example. The spray nozzles 5 are connected by atomization gas feeds and melt feed conduits (not shown). Additionally provided above the perforated plate 2 are one or more seed entry opening(s) 3 and, in the perforated plate 2, one or more granule exit opening(s) 4, with the distance between the seed entry opening 3 and the granule exit opening 4 defining a (theoretical) granule flow direction (I) (see arrow). The perforated plate 2 is (not shown) supplied with the fluidization medium from the bottom, for example air. The seed entry opening 3 permits the introduction of relatively small (smaller than the desired granule size) granule particles as seed particles into the fluidized bed granulator. Viewed in flow direction, the granulator interior also preferably comprises one or more dividing walls 7 that are each spaced apart from one another and extend in transverse direction of the granulator. The seed entry openings 3 may, viewed in granule flow direction, each be disposed between a first and a second dividing wall 7 at the granulator front wall 1a.3 and/or at the first granulator side wall 1a.1 and/or at the second granulator side wall 1a.2.

[0059] Via the spray nozzles 5 and the feeds (not shown) for the melt 6a and for atomization air 6b, the seed particles are contacted with melt droplets. This accretion results in continuous growth of the seed particles. The particles, as a result of the growth, preferably have a “raspberry-like” appearance at the microscopic level composed of a core with molten solidified (crystallized) droplets. The perforated plate 2 comprises growth zones (2a, 2a.sub.i, with i=1, 2, 3, . . . ) and cooling zones (2b, 2b.sub.i, with i=1, 2, 3, . . . ). In the growth zones (2a, 2a.sub.i, with i=1, 2, 3, . . . ) are disposed spray nozzles 5; in the cooling zones there are no spray nozzles (2b, 2b.sub.i, with i=1, 2, 3, . . . ) or, if appropriate, fewer spray nozzles 5 (not shown) are present than in the growth zones (2a, 2a.sub.i, with i=1, 2, 3, . . . ). The alternation of growth zones (2a, 2a.sub.i, with i=1, 2, 3, . . . ) and cooling zones (2b, 2b.sub.i, with i=1, 2, 3, . . . ) enables control of particle growth and of temperature distribution. This is useful especially for avoidance of the formation of biuret at high temperatures. Additionally disposed between the growth zones 2a and cooling zones 2b in flow direction are dividing walls 7; preferably, the dividing walls comprise passage openings (not shown). These may, for example, be slots in the region of the underside of the dividing walls 7, which arise, for example, in that the dividing walls 7 end above the perforated plate 2, and hence passage openings for the granule particles are present in flow direction from one zone to the next.

[0060] FIG. 2 shows a schematic top view of a fluidized bed granulator of the invention. The basic construction corresponds to the construction of a conventional fluidized bed granulator described above with reference to FIG. 1, and the features already described above will therefore not be repeated here. By comparison of the two FIGS. 1 and 2, it can be seen that, in the fluidized bed granulator of the invention, the granule exit opening is arranged at a distance in front of the granulator back wall 1a.4. Thus, the theoretical shortest distance between the granule exit opening 4 and the seed entry opening 3 and the granulator front wall 1a.3, given the same construction size of the fluidized bed granulator, is shorter in the case of the inventive solution than in the case of the conventional fluidized bed granulator according to FIG. 1, since, in the case of the latter, the granule exit opening 4 is in the region of the granulator back wall 1a.4 and hence, viewed from the seed entry opening 3, effectively at the opposite end of the fluidized bed granulator viewed in longitudinal direction.

[0061] In addition, the granule exit opening 4 is disposed within the perforated plate 2 and does not touch the granulator back wall 1a.4. The granule particles removed there then fall downward through the granule exit opening in the perforated plate 2, for example through a corresponding shaft. Subsequently, in a manner known per se, conveying devices and screens separate the different granule particle sizes from one another, and granule particles that do not meet the required specification are returned to the seed entry opening 3. These details are not shown in FIG. 2.

[0062] The granule exit opening 4, in the inventive configuration of multiple deflection plates 8, 8.1, 8.2, 8.3, is surrounded, for example, roughly in a U shape, in which case either no deflection plate 8 or (not shown) a deflection plate 8 with an opening is provided on the opposite side from the granulator back wall 1a.4. The deflection plates 8, 8.1, 8.2, 8.3 here result in circumventing flow with subsequent deflection of the granule particles present in the fluidized bed first past the granule exit opening 4 and then in reverse flow direction within the deflection plates 8, 8.1, 8.2, 8.3 into the granule exit opening 4. This reduces the distance between granule exit (granule exit opening 4) and return/seed inlet (seed entry opening 3) of the fluidized bed granulator, for example by about 20-50%. The movement of the granule exit opening 4 correspondingly reduces the height to be overcome by the conveying device and the building height of the granulation building, since the off-spec granule particles are recycled to the seed entry opening 3 in a region above the fluidized bed granulator, and the construction height of the apparatuses required for the purpose is reduced in the case of the inventive solution. This aspect will be elucidated in detail later on with regard to the schematic representations of FIGS. 6 and 7.

[0063] FIG. 3 shows a further schematic top view of a fluidized bed granulator of the invention. The fundamental construction corresponds to the construction described in FIG. 2. In the first granulator side wall 1a.1 there is disposed a conveying device 9. The conveying device 9 may alternatively be disposed in the second granulator side wall 1a.2. As a further alternative, one conveying device may be disposed in each of the two granulator side walls 1a.1, 1a.2. The flow direction F of the granule particles is indicated schematically by the arrows in FIG. 3. By contrast with prior art fluidized bed granulators, this permits, as described above, a much more compact design, especially in relation to the building height of the granulation building.

[0064] FIG. 4 shows a further schematic top view of an alternative configuration of the fluidized bed granulator of the invention. The basic construction corresponds to the construction described in FIG. 3. However, the granule exit opening 4 is disposed adjacent to the first granulator side wall 1a.1 and the conveying device 9 within the perforated plate 2. This arrangement reduces the transport distance to the conveying device 9.

[0065] Alternatively, a conveying device and a granule exit opening 4 may be disposed adjacent to the second granulator side wall 1a.2. A further alternative configuration is two granule exit openings each having a conveying device, each disposed adjacent to the first granulator side wall 1a.1 and to the second granulator side wall 1a.2.

[0066] FIG. 5 shows a further preferred schematic top view of the fluidized bed granulator of the invention. Indicated on the perforated plate 2, in significantly enlarged form compared to the real size, are schematic inclined openings 2c. In the installed perforated plate, the openings, for example, are of a size of 1 mm to 3 mm. For reasons of clarity, only individual inclined openings 2c are indicated. The flow direction of the air G or of the fluidization medium is indicated by way of example by the black arrow. The arrangement of the inclined openings 2c assists in steering the flow direction F of the granule particles.

[0067] A significant advantage of the inventive design of the fluidized bed granulator is elucidated below with reference to the schematic side views according to FIGS. 6 and 7. In each of the two drawings, the granulator front wall 1a.3 and the granulator back wall 1a.4 can be seen, between which the granule particles entering the granulator interior 1 at the seed entry opening 3 are conveyed in flow direction (longitudinal direction) toward the granule exit opening 4. Because this granule exit opening 4 is at the end of the granulator interior 1 in the conventional apparatus according to FIG. 6, the granule particles must cover the entire distance through the granulator interior before they reach the granule exit opening 4. Consequently, the schematically highly simplified conveying device 9 is disposed there, which must have a corresponding construction height in order to be able to recycle the off-spec granule particles via the screens disposed above the fluidized bed granulator as seed back to the seed entry opening 3.

[0068] In the case of the inventive solution, by contrast, the granule exit opening 4 and hence also the conveying device 9 proceeding therefrom is more in a middle region of the granulator side wall, at a considerable distance from the granulator back wall 1a.4, such that the distance over which the off-spec granule particles have to be returned to the granulator front wall 1a.3 and the seed entry opening(s) 3 disposed there is considerably shorter and, correspondingly, the construction height of the conveying device 9 and of the granulation building can also be significantly reduced.

LIST OF REFERENCE NUMERALS

[0069] 1 granulator interior [0070] 1a granulator interior walls [0071] 1a.1 first granulator side wall [0072] 1a.2 second granulator side wall [0073] 1a.3 granulator front wall [0074] 1a.4 granulator back wall [0075] 2 perforated plate [0076] 2a.sub.i growth zone [0077] 2b.sub.i cooling zone [0078] 2c inclined openings [0079] 3 seed entry opening(s) [0080] 4 granule exit opening(s) [0081] 5 spray nozzles [0082] 6a feeds for melt [0083] 6b feeds for atomization gas [0084] 7 dividing walls [0085] 8.sub.i deflection device/deflection plates [0086] 9 conveying device [0087] F flow direction of the granule particles [0088] G flow direction of the air or of the fluidization medium