fluidized bed type granulating apparatus or fluidized bed / jet bed type granulating apparatus

Abstract

A fluidized bed type or fluidized bed / airlift bed type granulating device which is a fluidized bed type or fluidized bed / airlift bed type granulating device for introducing seed particles of urea, an aqueous urea solution, and air to produce urea particles having an average particle diameter of 1 mm or more, the granulating device having a box-shaped granulating chamber composed of a bottom plate, a top surface portion, and a side surface portion, the inner wall surface of the granulating chamber being formed of a metal sheet, the granulating chamber having an exhaust port in the upper portion of the side surface portion or the top surface portion, the granulating chamber having a seed particle inlet for the seed particles of urea in the side surface portion or the top surface portion, the granulating chamber having a urea particle recovery port in the side surface portion, the aqueous urea solution being introduced from the bottom plate or the side surface portion, the air being introduced from the bottom plate or from the bottom plate and the side surface portion, at least a portion of the inner wall surface of the granulating chamber being subjected to rough surface processing, the arithmetic average roughness (Ra) (JIS B 0601:1994) of the concavo-convex of the rough surface processed surface being 0.35-5.0 μm, and the average interval (S) (JIS B 0601:1994) of the local peak tops of the concavo-convex being 2-300 μm.

Description

Technical Field

[0001] The present invention relates to a fluidized bed granulation apparatus or a fluidized bed / jet bed granulation apparatus that can be used to generate, for example, urea particles. Background Technology

[0002] As granulation devices for particles such as urea particles, fluidized bed granulation devices that use only a fluidized bed and fluidized bed / jet bed type granulation devices that combine a jet bed with a fluidized bed are known (Japanese Patent Application Publication No. 62-74443, Japanese Patent Application Publication No. 2007-167768, Japanese Patent No. 4455643, WO2006 / 094620).

[0003] In the granulation chamber of these granulation devices, a fluidized bed of urea particles driven by air, or a fluidized bed mixed with a jet bed, is formed. Urea seed crystals (hereinafter also called seed particles), which serve as the nuclei of the urea particles, and an aqueous urea solution are continuously supplied to this chamber, while urea particles of a predetermined size are granulated. However, in the granulation chamber, the phenomenon of dust (fine urea powder, such as fragments of urea particles) adhering and accumulating on the inner wall surface is generally a problem. This phenomenon is particularly pronounced on the inner wall surface above the fluidized bed. Dust that has accumulated to the boundary peels off in large chunks due to its own weight and falls, clogging the urea solution supply port or hindering the flow of the fluidized bed. If such a problem occurs, it necessitates stopping the operation of the granulation device to clean the interior of the granulation chamber, resulting in production losses. Therefore, eliminating and suppressing the adhesion and accumulation of dust on the inner wall of the granulation chamber becomes a key issue.

[0004] WO2015 / 014447A1 describes how applying an organosilicon compound to the inner wall of the granulation chamber can prevent dust accumulation and extend the cleaning interval of the granulation chamber.

[0005] Japanese Patent Application Publication No. 2008-230665 describes a powder handling apparatus in which predetermined irregularities are provided on the surface of steel in contact with the powder to improve the performance of the powder in peeling off and sliding off the steel surface, thereby preventing powder adhesion.

[0006] Japanese Patent Application Publication No. 2017-170408 describes a method for suppressing the adhesion or clogging of powder by sandblasting a mesh filter.

[0007] WO2018 / 007089 describes a method of applying vibrational displacement to the double inner walls of a granulator using a shaking member, thereby preventing or reducing the solidification of urea solution adhering to the inner wall to form a film, which can reduce the cleaning frequency and allow the equipment to work for a longer period of time. Summary of the Invention

[0008] The objective of this invention is to reduce the number of cleaning cycles of a fluidized bed granulation apparatus or a fluidized bed / jet bed granulation apparatus, thereby extending the continuous operating time, by suppressing dust adhesion to the inner wall of the granulation chamber where granulated particles such as urea particles are generated.

[0009] In one embodiment of the present invention, a fluidized bed granulation device or a fluidized bed / jet bed granulation device is provided, which is used to introduce urea seed particles, urea aqueous solution, and air to generate urea particles with an average particle size (based on sieve analysis methods JIS Z8815 and ASTM E11) of 1 mm or more.

[0010] The aforementioned fluidized bed granulation device or fluidized bed / jet bed granulation device has a box-shaped granulation chamber including a bottom plate, a top surface opposite the bottom plate, and a side surface between the bottom plate and the top surface. Additionally, a bottom surface opposite the bottom plate is located on the opposite side of the top surface.

[0011] The inner wall of the aforementioned granulation chamber is made of metal. It has an exhaust port above the top or side surface, an inlet for urea seed particles on the side or top surface, a urea particle recovery port on the side surface, an inlet for urea aqueous solution on the bottom plate or side surface, and an air inlet on the bottom plate or both the bottom plate and side surface.

[0012] At least a portion of the inner wall surface of the aforementioned granulation chamber is roughened.

[0013] The arithmetic mean roughness (Ra) of the aforementioned roughened surface (JIS B 0601:1994) is 0.35-5.0 μm, and the average interval (S) of the aforementioned local peaks of the roughness (JIS B 0601:1994) is 2-300 μm.

[0014] The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus of the present invention has its inner wall surface of the granulation chamber partially or entirely roughened to have a specific unevenness, thus making it difficult for dust to adhere and accumulate on the roughened surface. Therefore, the cleaning frequency of the granulation chamber can be reduced, allowing the granulation apparatus to operate continuously for extended periods. Attached Figure Description

[0015] Figure 1 This is a schematic front view of one embodiment of the fluidized bed / jet bed granulation apparatus according to the present invention, showing the state with the front side wall removed.

[0016] Figure 2 It is shown schematically. Figure 1 A top view of the granulation chamber of a fluidized bed / jet bed type granulation device, showing the top surface removed, omitting the internal fluidized bed / jet bed.

[0017] Figure 3 It is shown schematically. Figure 1 A side view of a fluidized bed / jet bed type granulation device, showing the state with the side walls removed.

[0018] Figure 4 This is a schematic front view of another embodiment of the fluidized bed / jet bed granulation apparatus according to the present invention, showing the state with the front side wall removed.

[0019] Figure 5 It is shown schematically. Figure 4 A top view of the granulation chamber of a fluidized bed / jet bed type granulation device, showing the top surface removed, omitting the internal fluidized bed / jet bed.

[0020] Figure 6 It is shown schematically. Figure 4 A side view of a fluidized bed / jet bed type granulation device, showing the state with the side walls removed. Detailed Implementation

[0021] (1) Figures 1-3 The fluidized bed / jet bed type granulation device shown in the figure

[0022] pass Figures 1-3 This invention describes an exemplary embodiment of the fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus of the present invention.

[0023] The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus of the present invention is an apparatus capable of generating urea particles with an average particle size of 1 mm or more by introducing, for example, urea seed particles, urea aqueous solution, and air. According to an example of the present invention, at least a portion of the inner wall surface of the granulation chamber is roughened to have a specific unevenness.

[0024] The average particle size can be determined by sieving using sieves that meet ASTM E11 specifications according to the sieve analysis method of JIS Z8815. For example, it can be determined by measuring the mass of the sample remaining on each sieve and recording the cumulative particle size distribution in a graph.

[0025] Therefore, when the granulation apparatus is a fluidized bed type granulation apparatus, the present invention can be applied to any apparatus that can form a fluidized bed in the granulation chamber as the urea particle generating mechanism. Similarly, when the apparatus is a fluidized bed / jet bed type granulation apparatus, the present invention can be applied to any apparatus that can form both a fluidized bed and a jet bed in the granulation chamber as the urea particle generating mechanism. Regarding the configuration other than the aforementioned inner wall surface of the granulation chamber, any of these configurations can include the same configuration as well-known granulation apparatuses or a modification of a portion of well-known granulation apparatuses.

[0026] Examples of well-known fluidized bed granulation apparatuses include those identical to or partially modified according to the first figure of Japanese Patent Application Publication No. 56-47181. Examples of well-known fluidized bed / jet bed granulation apparatuses include those similar to those in Japanese Patent Application Publication No. 2007-167768. Figure 3 Japanese Patent No. 4455643 Figure 1 Similar devices or devices with modifications for different purposes. Furthermore, fluidized bed granulation apparatuses or fluidized bed / jet bed granulation apparatuses to which the present invention can be applied include not only newly installed granulation devices but also existing granulation devices.

[0027] The following description refers to a fluidized bed / jet bed type granulation device (hereinafter, sometimes simply referred to as "granulation device") 1.

[0028] The granulation device 1 has a bottom part 11, a top part 12 opposite to the bottom part 11, and four side parts 13-16 (13, 14, 15, 16) disposed between the bottom part 11 and the top part 12. The interior of the granulation device 1 is divided into an upper internal space (granulation chamber) 20U and a lower internal space (air storage chamber) 20L (20L1 and 20L2) by a bottom plate 19 disposed between the bottom part 11 and the top part 12.

[0029] Regarding the side portions 13-16, the portion located above the base plate 19 forms side portions 13U-16U (13U, 14U, 15U, 16U), and the portion located below the base plate 19 forms 13L-16L (13L, 14L, 15L, 16L). Furthermore, hereinafter, when referred to as “U” along with the reference numeral of the constituent element, “U” means that the constituent element is located above the base plate 19 (top portion 12 side), and when referred to as “L” along with the reference numeral, “L” means that the constituent element is located below the base plate 19 (bottom portion 11 side).

[0030] In the box-shaped granulation chamber 20U, during the operation of the granulation device, a fluidized bed 50 and a jet bed 51 containing urea particles are formed on the bottom plate 19. The urea particles in the fluidized bed 50 and jet bed 51 flow in a violently pulsating manner, moving from the side portion 16U of the urea seed inlet line 25 (connected to the urea seed granules) towards the side portion 15U of the urea particle recovery line 35 (connected to the urea particle recovery line). Figure 2 (The white arrow in the image indicates the direction) the particle size increases while the particle moves slowly.

[0031] like Figure 2 As shown, the granulation chamber 20U has a rectangular planar shape, but is not limited to a rectangle. It can also be a square, a rectangle, or a shape that is a partial deformation of a square, or other shapes. The four side sides 13U-16U are composed of a first long side side 13U along the direction of movement of urea particles in the granulation chamber 20U, a second long side side 14U opposite to the first long side side 13U, a first short side side 15U, and a second short side side 16U opposite to the first short side side 15U.

[0032] The bottom plate 19, top surface 12, and four side surfaces 13U-16U constituting the granulation chamber 20U are formed of a metallic material (e.g., a plate-shaped metallic material). Regarding the top surface 12 and the four side surfaces 13U-16U, as long as the inner surface (the surface facing the granulation chamber 20U) is made of a metallic material, it is also possible for the opposite side (the outer surface of the metallic material) to be a layered structure made of a non-metallic material such as concrete.

[0033] The base plate 19, the top surface 12, and the four side surfaces 13U-16U can all be made of the same metal material (e.g., metal sheet), or they can be partially made of different metal sheets. In several examples, the metal material of the base plate 19, the top surface 12, and the four side surfaces 13U-16U is preferably partially or entirely made of iron or iron alloys (stainless steel, etc.).

[0034] On the second short side 16U of the granulation chamber 20U, at a position higher than the bottom plate 19, there is an inlet for urea seeds, and an inlet pipe 25 for urea seeds is connected.

[0035] An exhaust pipe 23 is connected to the top surface 12, and the connection port of the exhaust pipe 23 is the exhaust port 22 of the granulation chamber 20U. Most of the dust in the granulation chamber 20U is discharged to the outside along with the air through the exhaust port 22 and the exhaust pipe 23. The exhaust port 22 may also be formed at a position close to the height of the top surface 12 on any of the first long side surface 13U, the second long side surface 14U, the first short side surface 15U, or the second short side surface 16U.

[0036] In the granulation apparatus 1, below the granulation chamber 20U, there are a flow air storage chamber 20L1 and a jet air storage chamber 20L2 formed by a bottom part 11, side parts 13L-16L, partition wall 17 and bottom plate 19.

[0037] The base plate 19 is a porous plate with many small air holes 42. The outlet (upper end) of the jet pipe 41 through which the air for forming the jet bed passes is regularly arranged on the porous plate.

[0038] As a base plate 19 formed by a perforated plate with outlets of jet pipes 41 through which jet air passes in a regular arrangement, for example, the one disclosed in Japanese Patent No. 4455643 can be used. Figure 4 The perforated plate (equivalent to the present invention) Figure 1 The base plate 19), and the perforated plate of Figure 9 of this publication (equivalent to the base plate of the present invention) Figure 1 The base plate 19), the communiqué Figure 5 , Figure 6 The porous plates shown or modified porous plates are shown in the figure.

[0039] In such Figure 1 In the case of such a granulation apparatus 1, air for forming the fluidized bed is temporarily supplied from the flow air inlet line 40 to the flow air storage chamber 20L1 located below the base plate 19, and then introduced into the granulation chamber 20U through the air holes 42 of the base plate 19. Jet air is temporarily supplied from the jet air inlet line 45 to the jet air storage chamber 20L2 located below the flow air storage chamber 20L1, and then introduced into the granulation chamber 20U through the jet pipe 41.

[0040] Air for jetting is supplied from the outlet of jet pipes 41 regularly arranged in the bottom plate 19 of the granulation chamber 20U, forming a jet bed 51 in the fluidized bed 50, which is a sparse space for the presence of particles. Urea aqueous solution is introduced from the urea aqueous solution inlet line 31 and sprayed into the jet bed 51 in the granulation chamber 20U from the urea aqueous solution spray nozzle 32 located near the center of the outlet surface of the jet pipe 41.

[0041] In the jet bed 51, particles are accelerated by the jet of air, leap into the space above the fluidized bed 50 as shown by arrow 48, lose momentum and fall into the fluidized bed 50, being drawn into the surrounding jet bed 51, where they are again sprayed with droplets of urea aqueous solution. The sprayed urea droplets repeatedly adhere to and dry, layering onto the surface of the urea particles in the jet bed 51, thereby supplying seed granules in the granulation chamber 20U to grow into urea particles of a predetermined size.

[0042] In Figure 1 In the example, such as Figure 2 and Figure 3As shown, six injection nozzles 32 are arranged along the Y direction, and three injection nozzles 32 are arranged along the Z direction, which is orthogonal to the Y direction. The number of injection nozzles 32 can be adjusted according to the production volume of urea particles generated in the granulation device 1, and the arrangement of the injection nozzles 32 can be adjusted according to the shape of the granulation device.

[0043] The area where the urea aqueous solution is disposed is the area enclosed by the region shown by the first long side side portion 13Ua and the region shown by the second long side side portion 14Ua. In the area enclosed by the region shown by the first long side side portion 13Ub and the region shown by the second long side side portion 14Ub, no spray nozzle 32 is disposed.

[0044] The proportion of the Y-direction length of the region 13Ua occupied by the Y-direction length of the first long side side portion 13U (or the Y-direction length of the region 14Ua occupied by the Y-direction length of the second long side side portion 14U) is determined by comprehensively considering the number of urea aqueous solution spray nozzles 32 provided in the granulation device or the temperature requirements of the urea particles recovered from the urea particle recovery pipeline 35, the shape of the building where the granulation device is located, etc.

[0045] On the first short side 15U, there is an outlet for urea particles, which is connected to a urea particle recovery line 35. Among the urea particles flowing out to the urea particle recovery line 35, particles that enter within a predetermined particle size range are separated by a sieve or the like and sent to the next process as products. Particles smaller than this range can be fed back to the granulation chamber 20U from the urea seed particle inlet line 25 as is. In addition, particles that exceed this range can be crushed into smaller particles using a pulverizer or the like and then fed back to the granulation chamber 20U from the urea seed particle inlet line 25.

[0046] Particles entering the predetermined particle size range can also be pulverized into smaller particles as needed, and then supplied again from the urea seed inlet line 25 to the granulation chamber 20U.

[0047] Part or all of the inner wall surface of the granulation chamber 20U is roughened. Here, the inner wall surface refers to the inner wall surface of the bottom plate 19, the side portions 13U-16U and the top portion 12 that constitute the granulation chamber 20U.

[0048] When a portion of the inner wall surface is roughened, it is preferable that at least a portion of the height range from the bottom plate 19 to the top surface 12 of the side portions 13U and 14U is roughened, and more preferably a portion of the height range from the bottom plate 19 to the top surface 12 of the side portions 13U-16U is roughened. The side portions roughened in this way can be the inlet of seed granules without urea or the outlet of urea particles. In the side portions 13U-16U, the height range of the roughened portion preferably includes the height 53 (X-direction range) above the bottom plate 19 where the fluidized bed 50 is formed during operation of the granulation apparatus.

[0049] In the side portions 13U-16U, the range including the height 53 where the fluidized bed 50 is formed during operation is from the bottom plate 19 to the height 53 where the fluidized bed 50 is formed during operation and the range on the top portion 12 side which is higher than the height 53 where the fluidized bed 50 is formed during operation. The latter range is preferably 1 to 10 times the height 53 where the fluidized bed 50 is formed during operation, and more preferably 3 to 9 times.

[0050] The height 53 of the fluidized bed 50 formed during operation varies depending on the size of the granulation device 1 or the operating conditions, but is preferably in the range of 100-1000 mm.

[0051] When a portion of the inner wall surface of the granulation chamber 20U is roughened, the area roughened in the side portions 13U and 14U preferably includes the area where the urea aqueous solution injection nozzles 32 are provided in the direction (Y direction) from the side portion 16U toward the side portion 15U. Specifically, for example, as Figure 2 As shown in the figure, the preferred regions are the regions 13Ua of the first long side surface portion and the region 14Ua of the second long side surface portion, which are opposite to the region where the jet nozzle 32 is disposed.

[0052] When a portion of the inner wall surface of the granulation chamber 20U is roughened, it is preferable that, in addition to at least a portion of the side portions 13U-16U described above, a portion of the top portion 12 is also roughened. When a portion of the top portion 12 is roughened, the area roughened in the top portion 12 is more preferably a peripheral portion with a width of 100-1000 mm along the boundary line between the top portion 12 and the side portions 13U-16U, and a peripheral portion with a width of 100-1000 mm along the boundary line between the top portion 12 and the exhaust port 22.

[0053] The arithmetic mean roughness (Ra) of the roughened surface finish (unevenness) of the inner wall surface of the granulation chamber 20U (JIS B 0601:1994) is 0.35-5.0 μm, and the average interval (S) of the local peaks of the aforementioned unevenness (JIS B 0601:1994) is 2-300 μm, preferably 2-50 μm. If the roughened surface finish (unevenness) of the inner wall surface is within the aforementioned range, the dust adhesion suppression effect on the roughened surface is highest.

[0054] In the granulation chamber 20U, when a portion of the inner wall surface of the side portion 13U-16U is roughened, the roughened surface can include a first roughened surface and a second roughened surface processed into two different roughened surface morphologies.

[0055] The range of the first roughened surface is at least in the height direction of the side surface 13U and the side surface 14U. Figure 1 The range extends along the X direction from the base plate 19 to the height 53 where the fluidized bed 50 is formed during operation, and to the upper surface side that is higher than the aforementioned height 53 where the fluidized bed 50 is formed during operation. The latter range is preferably 1 to 10 times the height 53 where the fluidized bed 50 is formed during operation, and more preferably 3 to 9 times the height 53 where the fluidized bed 50 is formed during operation.

[0056] Furthermore, the range of the aforementioned first roughened surface preferably includes the side portions 13U and 14U in the direction from the side portion 16U toward the side portion 15U. Figure 2 The area in the Y direction where the urea aqueous solution injection nozzle 32 is disposed is preferably the area of ​​the first long side side portion 13Ua and the area of ​​the second long side side portion 14Ua opposite to the area where the urea aqueous solution injection nozzle 32 is disposed.

[0057] The range of the second rough surface is the range of the inner wall surface of the side portion 13U-16U and the top portion 12 of the granulation chamber 20U, excluding the first rough surface, and ideally, it is adjacent to the first rough surface.

[0058] The arithmetic mean roughness (Ra1) (JIS B0601:1994) of the roughness condition (unevenness) of the first rough surface is 0.35-5.0 μm, and the average interval (S1) (JIS B 0601:2001) of the aforementioned unevenness local peaks is 2-300 μm, preferably 2-50 μm. The arithmetic mean roughness (Ra2) (JIS B 0601:1994) of the roughness condition (unevenness) of the second rough surface preferably satisfies the relationship Ra1>Ra2 with respect to the aforementioned Ra1.

[0059] The preferred relationship between Ra1 and Ra2 is Ra1 / Ra2 = 1-35. The relationship between the average interval S1 of the peaks of the first roughened surface and the average interval S2 of the peaks of the second roughened surface is S1 / S2 = 1-1000, preferably 3-100. Furthermore, the roughness measurements of Ra and S can be performed using a shape analysis laser microscope such as the VK-X250 manufactured by KEYENCE.

[0060] As a method for roughening surfaces, various well-known sandblasting processes or modified sandblasting processes can be used (for example, the methods described in Japanese Patent Application Publication No. 2017-170408 "Surface Treatment Method for Mesh Filter and Mesh Filter" or Japanese Patent Application Publication No. 2012-040744 "Surface Treatment Method for Metal Mold and Metal Mold Surface Treated by the Foregoing Method"). In addition to sandblasting, roughening surfaces can also be performed by chemical grinding (acid pickling, strong alkali), sandpaper, polishing, electrolytic grinding, passivation coating treatment, coating (PVD, CVD, fluorine), etc.

[0061] When applying the aforementioned roughening method to a newly installed granulation device, it is possible to use a method that directly roughens the inner wall surface of the granulation chamber 20U or to attach a roughened metal sheet to the inner wall surface of the granulation chamber 20U by means of welding or bolt fastening.

[0062] Furthermore, when applying the aforementioned roughening method to an existing granulation apparatus, the same method as described above can be used to directly roughen the inner wall of the granulation chamber, or a fixing method such as welding or bolting can be used to attach a roughened metal sheet to the inner wall of the granulation chamber 20U. Alternatively, the existing wall of the granulation chamber 20U can be removed and replaced with a roughened metal sheet.

[0063] (2) Figures 4-6 The fluidized bed / jet bed type granulation device shown in the figure

[0064] according to Figures 4-6 Other embodiments of the fluidized bed / jet bed type granulation apparatus of the present invention will be described. Figures 4-6 Among the constituent elements shown, and Figures 1-3 Identical parts are assigned the same number.

[0065] exist Figures 4-6 In the fluidized bed / jet bed type granulation apparatus 1A shown, the following high-pressure spray nozzle method is used with... Figures 1-3The fluidized bed / jet bed type granulation device 1 shown in the figure is different: both the urea aqueous solution introduced from the urea aqueous solution inlet line 31 and the high-pressure air introduced from the high-pressure air inlet line 60 are introduced into the injection nozzle 61, and the mixed gas of urea aqueous solution and high-pressure air is injected into the granulation chamber 20U from the injection nozzle 61 of the bottom plate 19 formed by the perforated plate provided in the granulation chamber 20U.

[0066] For example, as described in WO2006 / 094620, the nozzle 61 for spraying the mixture of urea aqueous solution and air can also be provided in any one of the side portions 13U-16U of the granulation chamber 20U.

[0067] In this example, such as Figure 5 As shown, 11 injection nozzles 61 are arranged along the Y direction, and 6 injection nozzles 61 are arranged along the Z direction, which is orthogonal to the Y direction. The number of injection nozzles 61 can be adjusted according to the production volume of urea particles generated in the granulation device 1A, and the arrangement of the injection nozzles 61 can be adjusted according to the shape of the granulation device.

[0068] The area where multiple spray nozzles 61 are configured is the area sandwiched between the region 13Ua of the first long side side and the region 14Ua of the second long side side. No spray nozzles 61 are configured in the area sandwiched between the region 13Ub of the first long side side and the region 14Ub of the second long side side.

[0069] The proportion of the Y-direction length of the region 13Ua occupied by the Y-direction length of the first long side side 13U (or the Y-direction length of the region 14Ua occupied by the Y-direction length of the second long side side 14U) is determined by comprehensively considering the number of spray nozzles 61 provided in the granulation device, the temperature requirements of the urea particles recovered from the urea particle recovery pipeline 35, the shape of the building where the granulation device is located, etc.

[0070] Part or all of the inner wall surface of the granulation chamber 20U is roughened. Here, the inner wall surface refers to the inner wall surface of the bottom plate 19, the four side surfaces 13U-16U and the top surface 12 that constitute the granulation chamber 20U.

[0071] When a portion of the inner wall surface is roughened, it is preferable that at least a portion of the height range from the bottom plate 19 to the top surface 12 in at least the side portions 13U and 14U is roughened, and more preferably a portion of the height range from the bottom plate 19 to the top surface 12 in the side portions 13U-16U is roughened. The height direction of the side portions 13U-16U that are roughened ( Figure 4 The range of the X direction can be related to Figures 1-3 The situation is the same as that of granulation device 1.

[0072] The height 53 of the fluidized bed 50 formed during the operation of the granulation device varies depending on the size of the granulation device 1A or the operating conditions, but the height is preferably in the range of 100-1000 mm.

[0073] The transverse direction (orthogonal to the X direction) of the inner wall surface of the granulation chamber 20U where roughening is performed. Figure 5 The range (in the Y direction) preferably includes the lateral direction range of the spray nozzle 61 in which the urea aqueous solution is disposed, and more specifically, it is preferably the range of the region 13Ua of the first long side side portion and the region 14Ua of the second long side side portion opposite to the range in which the spray nozzle 61 is disposed.

[0074] Furthermore, when a portion of the inner wall surface of the granulation chamber 20U is roughened, it is preferable that, in addition to at least a portion of the side surfaces 13U-16U of the four sides mentioned above, a portion of the top surface 12 is also roughened. When a portion of the top surface 12 is roughened, the range of roughening of the top surface 12 can be [missing information]. Figures 1-3 The situation is the same as that of granulation device 1.

[0075] The surface roughening condition (unevenness) of the inner wall surface of the granulation chamber 20U, which undergoes roughening, can be compared with... Figures 1-3 The situation is the same as that of granulation device 1.

[0076] When a portion of the inner wall surface of the side portion 13U-16U of the granulation chamber 20U is roughened, this roughened surface can be formed into a first roughened surface and a second roughened surface with two different roughened surface morphologies. The ranges of the first roughened surface and the second roughened surface can be respectively... Figures 1-3 The situation is the same as that of granulation device 1. Furthermore, the roughness (unevenness) of the first and second roughened surfaces can be respectively compared with... Figures 1-3 The situation is the same as that of granulation device 1.

[0077] The roughening method and its applicability to the granulation chamber 20U can be respectively compared with... Figures 1-3 The situation is the same as that of granulation device 1.

[0078] (3) Regarding the operation method of the granulation device and the effect of roughening the inner wall surface of the granulation chamber.

[0079] by Figures 1-3 Taking the granulation device 1 shown in the figure as an example, the operation method of the granulation device (the method of generating urea particles using the granulation device 1) will be explained below. The effect of roughening the inner wall surface of the granulation device will also be explained below.

[0080] The operating method and operating conditions of the granulation apparatus 1 are not particularly limited as long as they are methods that can generate urea particles using a fluidized bed. For example, in addition to the operating method described in Japanese Patent No. 4455643, the operating methods described in Japanese Patent Publication No. 04-063729, Japanese Patent Application Publication No. 10-216499 and Japanese Patent Application Publication No. 11-137988, or operating methods that modify their operating methods, can be implemented.

[0081] about Figure 1 The inner wall surface of the granulation chamber 20U of the granulation apparatus 1 shown in the figure, at least the side portions 13U and 14U along the direction of movement of urea particles in the fluidized bed 50, in the top portion 12, the side portions 13U-16U (first long side portion 13U, second long side portion 14U, first short side portion 15U, second short side portion 16U) that are in contact with the fluidized bed 50, and the bottom plate 19, are roughened, such that the state (unevenness) of the roughened surface is in the range of Ra=0.35-5.0 μm and S=2-300 μm in the range from the bottom plate 19 to the height 53 of the fluidized bed 50 formed during operation and in the range of 1-10 times the height 53 of the fluidized bed 50 formed during operation on the top portion 12 side above that range.

[0082] Inside the granulation chamber 20U of the granulation apparatus 1, urea seeds are continuously supplied from the seed granule inlet line 25 connected to the side portion 16U, and flowing air is continuously introduced from the flowing air inlet line 40 via the flowing air storage chamber 20L1 through the vent holes 42 of the bottom plate 19, which is a porous plate, forming a fluidized bed 50 on the bottom plate 19 in a violently jumping manner.

[0083] Furthermore, by continuously supplying jet air from the outlet of the jet pipe 41 regularly arranged on the bottom plate 19 through the jet air inlet line 45 and the jet air storage chamber 20L2, a jet bed 51 with a sparse space of particles is formed in the fluidized bed 50.

[0084] Simultaneously, the urea aqueous solution is continuously sprayed from the injection nozzle 32 of the urea aqueous solution, which is connected to the inlet pipe 31 and located near the center of the outlet surface of the jet pipe 41. In the jet bed 51, the urea particles sprayed with urea solution fly up as shown by arrow 48, lose momentum, and fall into the fluidized bed 50, where they are entrained by the surrounding jet bed 51 and sprayed with urea aqueous solution droplets again.

[0085] By mixing the fluidized bed 50 with the jet bed 51, the urea aqueous solution sprayed from the urea aqueous solution spray nozzle 32 uniformly and efficiently adheres to the surface of the urea seed particles. The urea particles gradually increase in size and move from the side portion 16U toward the side portion 15U, and are recovered from the urea particle recovery line 35 connected to the side portion 15U.

[0086] In the recovered urea particles, urea particles of different sizes are mixed together. Particles within a predetermined particle size range are separated using sieves or similar methods and sent as a product to the next process. Particles smaller than the predetermined range can be fed back into the granulation chamber 20U from the aforementioned urea seed particle inlet line 25 as is. Particles exceeding the predetermined range can be pulverized into smaller particles using a pulverizer or similar device and then fed back into the granulation chamber 20U from the aforementioned urea seed particle inlet line 25. Particles within the predetermined particle size range can also be pulverized into smaller particles according to the required number of seed particles and then fed back into the granulation chamber 20U from the aforementioned urea seed particle inlet line 25.

[0087] During the granulation process of urea particles in the granulation device 1, fine fragments are generated in the granulation chamber 20U due to collisions between flowing urea particles or between urea particles and the wall of the granulation chamber 20U; small droplets of urea aqueous solution sprayed from the urea aqueous solution spray nozzle 32 solidify without adhering to the urea particles; and fine fragments generated when recycled urea particles larger than a predetermined size are crushed and mixed with the seed particles from the urea seed particle inlet line 25. These are all fine urea powders with an average particle size of 1 mm or more (based on the average particle size of sieve test methods JIS Z8815 and ASTM E11) (e.g., less than 400 μm) that are much smaller than the average particle size of the urea to be produced (based on the average particle size of sieve test methods JIS Z8815 and ASTM E11). Such fine urea powders are generally referred to as dust.

[0088] The dust generated in the granulation chamber 20U is small and light, and is therefore basically discharged along with the air from the exhaust pipe 23 connected to the exhaust port 22 along with the airflow in the granulation chamber 20U. However, due to the influence of local airflow speed or direction, turbulence intensity, etc., some dust is not discharged and adheres and accumulates on the inner wall of the granulation chamber 20U. If the adhesion and accumulation continues and the amount reaches a limit, the dust will peel off in large pieces due to its own weight and fall down, which will cause problems such as clogging of the urea aqueous solution spray nozzle 32 or obstruction of the flow of the fluidized bed 50.

[0089] To eliminate and suppress this problem, the present invention performs a roughening process on the inner wall surface of the granulation chamber 20U, on areas where dust adhesion and accumulation previously occurred, thereby significantly suppressing dust adhesion and accumulation. These areas where dust adhesion and accumulation previously occurred refer to the areas described in "(1)". Figures 1-3The description of the fluidized bed / jet bed type granulation apparatus shown in the document details the scope of roughening. Even if the location where dust adheres and accumulates on the inner wall of the granulation chamber 20U differs from, or is predicted to be different, the roughening process can be performed only at such locations.

[0090] According to the present invention, dust is difficult to adhere to and accumulate on the inner wall surface of the granulation chamber 20U, so dust adhesion and accumulation will not occur at all, or even if it does occur, the limit of the possible amount of dust adhesion and accumulation is reduced, so that the dust will peel off as small pieces of no size due to its own weight before it can greatly carry out its adhesion and accumulation.

[0091] Therefore, by extending the interval between water washing operations on the inner wall of the granulation chamber 20U, which are typically performed to remove dust that is obviously attached and accumulated on the inner wall of the granulation chamber 20U or dust that hinders operation as large pieces peel off and fall, the operating efficiency of the granulation unit can be improved and maintenance costs can be reduced.

[0092] For example, under the same operating conditions, in a granulation apparatus with a conventionally mirror-finished inner wall surface, the cleaning interval is about 0.5 to 1 month. In contrast, in the granulation apparatus 1 of the present invention, the cleaning interval can be extended to about 1 to 3 months.

[0093] Even if Figures 4-6 The granulation apparatus 1A shown herein, or other fluidized bed granulation apparatuses, share the common feature of dust easily adhering and accumulating on the inner wall of the granulation chamber. Therefore, the present invention can be applied to obtain [the desired result]. Figures 1-3 The granulation device 1 shown in the figure has the same effect.

[0094] Industrial availability

[0095] The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus of the present invention can be used as an apparatus for manufacturing urea particles with an average particle size of 1 mm or more.

[0096] Symbol Explanation

[0097] 1.1A Granulation Unit

[0098] 11. Bottom surface of the granulation unit

[0099] 12 Top face

[0100] 13-16 Side profile

[0101] 17. Partition wall

[0102] 19. Base Plate

[0103] 20U Granulation Chamber

[0104] 20L1 Mobile Air Storage Chamber

[0105] 20L2 Jet Air Storage Chamber

[0106] 22 Exhaust port

[0107] 23 Exhaust pipe

[0108] 25. Seed delivery line for urea.

[0109] 31. Urea aqueous solution inlet line

[0110] 32. Urea aqueous solution injection nozzle

[0111] 35. Urea particle recovery pipeline

[0112] 40. Air inlet line for flow

[0113] 41 Jet tube

[0114] 42 Air holes in base plate 19

[0115] 45. Air inlet line for jetting

[0116] 48 Flying urea particles

[0117] 50 fluidized bed

[0118] 51 Jet Bed

[0119] 53. Height of the fluidized bed

[0120] 60 High-pressure air inlet line

[0121] 61. Injection nozzle.

Claims

1. A fluidized bed granulation device or a fluidized bed / jet bed granulation device, which is used to introduce urea seed particles, urea aqueous solution, and air to generate urea particles with an average particle size of 1 mm or more based on sieving tests JIS Z8815 and ASTM E11, wherein... The fluidized bed granulation device or fluidized bed / jet bed granulation device has a box-shaped granulation chamber including a bottom plate, a top surface opposite the bottom plate, and a side surface between the bottom plate and the top surface. Additionally, a bottom surface opposite the bottom plate is located on the opposite side of the top surface. The inner wall of the granulation chamber is formed of metal. It has an exhaust port above the top or side surface, an inlet for urea seed granules on the side or top surface, an outlet for urea particles on the side surface, an inlet for urea aqueous solution on the bottom plate or the side surface, and an air inlet on the bottom plate or both the bottom plate and the side surface. At least a portion of the inner wall surface of the granulation chamber is roughened, and the roughened surface includes a first roughened surface and a second roughened surface processed into two different roughened surface morphologies. The arithmetic mean roughness Ra of any of the first rough surface and the second rough surface, based on JIS B 0601:1994, is 0.35-5.0 μm, and the average interval S of the local peaks of the rough surface, based on JIS B 0601:1994, is 2-300 μm.

2. The fluidized bed granulation device or fluidized bed / jet bed granulation device according to claim 1, wherein, At least a portion of the side surface between the base plate and the top surface is roughened.

3. The fluidized bed granulation device or fluidized bed / jet bed granulation device according to claim 1 or 2, wherein, At least a portion of the side surface between the base plate and the top surface is roughened, and consequently a portion of the top surface is roughened.

4. The fluidized bed granulation device or fluidized bed / jet bed granulation device according to claim 1 or 2, wherein, At least a portion of the side surface between the base plate and the top surface is roughened. The height range of the side surface to be roughened is the range of the height of the fluidized bed formed in the granulation chamber during the operation of the granulation device, on the top surface side of the upper side of the base plate.

5. The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus according to claim 1 or 2, wherein, At least a portion of the side surface between the base plate and the top surface is roughened. The side portion subjected to the roughening process is a side portion that does not have an inlet for the urea seed particles or an outlet for the urea particles, and is the range opposite to the range in which the urea aqueous solution is provided in the base plate.

6. The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus according to claim 1 or 2, wherein, At least a portion of the side surface between the base plate and the top surface is roughened. The height range of the side surface to be roughened includes the height range of the fluidized bed formed in the granulation chamber during the operation of the granulation device, on the top surface side of the upper side of the base plate. The range including the height range of the fluidized bed formed in the granulation chamber during operation is the range up to the height of the fluidized bed formed in the granulation chamber during operation, and the range in the height direction of the top surface side above the height of the fluidized bed. The range in the height direction of the top surface side above the height where the fluidized bed is formed is 1 to 10 times the height where the fluidized bed is formed.

7. The fluidized bed granulation device or fluidized bed / jet bed granulation device according to claim 6, wherein, The inner wall surface of the top surface side, which is located above the height of the fluidized bed formed in the granulation chamber during operation, has a first roughened surface in a range of 1 to 10 times the height of the fluidized bed. Its arithmetic mean roughness Ra1, based on JIS B 0601:1994, is 0.35-5.0 μm, and the average interval S1 of the local peaks of the roughened surface, based on JIS B 0601:1994, is 2-300 μm. The second roughened surface is located in a range that includes the top surface side which is higher than the first roughened surface, and the arithmetic mean roughness Ra2 of the inner wall surface of the second roughened surface, based on JIS B 0601:1994, satisfies the relationship Ra1>Ra2 with Ra1.

8. The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus according to claim 7, wherein, The arithmetic mean roughness Ra1 of the inner wall surface of the first roughened surface, based on JIS B 0601:1994, and the average interval S1 of the local peaks of the unevenness of the inner wall surface, based on JIS B 0601:1994, and The arithmetic mean roughness Ra2 of the inner wall surface of the second roughened surface, based on JIS B 0601:1994, and the average interval S2 of the local peaks of the unevenness of the inner wall surface, based on JIS B 0601:1994, are... Ra1 and Ra2 satisfy the relationship that Ra1 / Ra2 is 1-35, and S1 and S2 satisfy the relationship that S1 / S2 is 1-1000.

9. The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus according to claim 7 or 8, wherein, Ra1 is 0.35-5.0 μm, and the average interval S1 is 2-50 μm.

10. The fluidized bed granulation apparatus or fluidized bed / jet bed granulation apparatus according to claim 1 or 2, wherein, The granulation chamber has a bottom plate formed by a perforated plate with outlets of multiple jet tubes regularly arranged. The inlet of the urea seed granules is connected to the side of the top surface of the bottom plate. The spray nozzle for spraying the urea aqueous solution is arranged near the center of the outlet surface of the jet tubes. The urea aqueous solution, together with the jet of air ejected from the outlet of the jet tubes, is sprayed into the fluidized bed formed in the granulation chamber.

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