Granular material drying device

Abstract

The purpose of the present invention is to propose a granular material drying device with which uniform drying is possible, in which adhesion to a perforated plate, which is a turning mechanism, does not readily occur, and for which a compact device design is possible. This granular material drying device comprises a cylindrical container, a granular material and heated gas introduction pipe, a perforated plate that forms a swirling updraft inside the cylindrical container, and a granular material and heated gas discharge pipe. The granular material drying device is provided with a granular material circulation path 15 in which one opening end 15a opens at a portion below the portion of connection of the granular material and heated gas discharge pipe and along an inner peripheral wall surface of the cylindrical container, and the other opening end 15b opens near the center of the perforated plate that forms the swirling updraft inside the cylindrical container.

Description

Drying apparatus for powders and granules

[0001] The present invention relates to a drying apparatus for powders and granules. More specifically, the present invention relates to a drying apparatus for powders and granules that dries powders and granules by forming a swirling upward airflow inside a cylindrical container.

[0002] The applicant in this case aimed to provide a new powder and granular material drying apparatus that possesses the advantages of an airflow dryer. Furthermore, the applicant aimed to improve the drying state by dispersing the powder and granular material well, increasing the residence time, and improving the drying condition in an airflow drying type powder and granular material drying apparatus. To solve these problems, the applicant created the drying apparatus disclosed in Patent Document 1 and filed a patent application.

[0003] The drying apparatus disclosed in Patent Document 1 has the following configuration. Specifically, this drying apparatus comprises a cylindrical container having a horizontal cross-section of any height with a concentric internal space. An introduction pipe for introducing powder and heated gas is connected to the lower part of this cylindrical container. Furthermore, it is equipped with a swirling mechanism that causes the introduced heated gas to swirl upward within the cylindrical container. An exhaust pipe for discharging the powder and heated gas is connected to the upper part of the cylindrical container. In this drying apparatus, the entire circumference of the lower side wall of the cylindrical container is made of a perforated plate. Multiple nozzles are formed in this perforated plate, facing in one direction tangential to the cylindrical container. Furthermore, the area around this perforated plate is covered by a container, to which the introduction pipe for heated gas is connected. These configurations form the swirling mechanism for heated gas described above. A powder and granular material drying apparatus with such a configuration is the gist of Patent Document 1 (see Claim 14 of Patent Document 1).

[0004] According to the drying device disclosed in Patent Document 1, the granular material moves upward from below while being carried by the swirling upward airflow caused by the heated gas. Also, the granular material receives an upward force and a centrifugal force during the movement. As a result, the wet and lumped granular material is also crushed and dried in a well-dispersed state. Also, in this drying device, since the granular material rises while swirling inside the cylindrical container, the moving distance of the granular material becomes longer. Also, a speed difference occurs between the granular material and the heated gas due to friction with the inner wall surface of the container. Therefore, the heat exchange amount increases, and the drying state of the granular material can be further improved. Furthermore, in this drying device, the centrifugal force received by the granular material from the swirling upward airflow is greater for wet and dense granular material. Therefore, the granular material immediately after introduction or the granular material with a large amount of moisture swirls near the inner peripheral wall surface of the cylindrical container for a long time. As a result, the residence time becomes longer and the drying state becomes good. Also, the granular material can be dried uniformly.

[0005] Japanese Patent No. 3145412

[0006] However, the granular material drying device disclosed in Patent Document 1 also had the following problems. First, large or flat granular materials that are strongly affected by the airflow may be carried by the airflow and discharged early without being sufficiently dried. For this reason, the uniformity of drying may be impaired. Second, the granular material with a high moisture content immediately after introduction was likely to adhere to the porous plate provided on the lower side wall of the cylindrical container. This deposit may be altered by heating and then peeled off and mixed into the dried product. Third, although this drying device was relatively compact as a pneumatic dryer, it still required a certain amount of space for installation. Therefore, further miniaturization was desired.

[0007] The present invention has been made to solve the above problems. An object of the present invention is to provide a drying device for granular materials that realizes more uniform drying, suppresses adhesion to the porous plate which is a swirling mechanism, and enables a more compact device design.

[0008] To achieve the above-mentioned objectives, the present invention provides a drying apparatus for powders and granules as described in [1] to [7] below. [1] A drying apparatus for powders and granules comprising a cylindrical container having a concentric internal space with a horizontal cross-section of any height, an introduction pipe for powders and a pipe for heated gas connected to the lower part of the cylindrical container, a swirling mechanism that causes the heated gas introduced from the introduction pipe to become a swirling upward airflow within the cylindrical container, and discharge pipes for powders and heated gas connected to the upper part of the cylindrical container, wherein the lower side wall of the cylindrical container is made of a perforated plate with a plurality of nozzles formed thereon, whose openings are arranged to face one direction tangential to the cylindrical container, the periphery of the perforated plate is covered by a container, and the introduction pipe for heated gas is connected to the container, and the lower wall of the cylindrical container is made of a perforated plate with a plurality of nozzles formed thereon, whose openings are arranged to face one direction substantially circumferentially on a concentric circle with the cylindrical container, the lower part of the perforated plate is covered by a container, and the introduction pipe for heated gas is also connected to the container, thereby constituting the swirling mechanism for heated gas, A drying apparatus for powders and granules, characterized in that one open end of the powders and granules is located below the connection point of the discharge pipe for the heating gas and along the inner circumferential wall surface of the cylindrical container, and the other open end is located near the center of the perforated plate forming the lower wall of the cylindrical container. [2] The drying apparatus for powders and granules according to [1], characterized in that a ring-shaped member is provided in a part of the cylindrical container located directly above the opening of one open end of the circulation passage, which blocks the powders and granules that have swirled up along the inner circumferential wall surface of the cylindrical container. [3] The drying apparatus for powders and granules according to [1], characterized in that the side wall of a cylindrical container located below the connection part of the discharge pipe for the powders and granules and heated gas is made of a porous plate having a plurality of nozzles arranged so that the opening faces the same direction as the direction of rotation of the swirling upward airflow formed inside the cylindrical container by the swirling mechanism, the periphery of the porous plate is covered with a container, and the introduction pipe for the heated gas is also connected to the container, thereby forming an air ring at that position that blocks the powders and granules that have swirled upward along the inner circumferential wall surface of the cylindrical container, and one open end of the circulation path is opened along the inner circumferential wall surface of the cylindrical container at the part where the air ring is formed.[4] The powder drying apparatus according to any one of [1] to [3] above, characterized in that the circulation path comprises a straight pipe member arranged along the axis of the cylindrical container and a guide member connected to the upper end of the straight pipe member, the inlet of the guide member opens in a direction opposite to the swirling upward airflow formed inside the cylindrical container at a point below the connection of the discharge pipes for the powder and heated gas and along the inner circumferential wall surface of the cylindrical container, and the lower end of the straight pipe member opens directly above the perforated plate constituting the lower wall of the cylindrical container. [5] The powder drying apparatus according to any one of [1] to [4] above, characterized in that the cylindrical container is a cylindrical container having an internal space in which the horizontal cross-section is enlarged in the middle of its axial direction compared to other parts and is concentric, and one end of the circulation path is opened at a point above the enlarged portion and below the connection of the discharge pipes for the powder and heated gas. [6] A drying apparatus for powders and granules according to any one of [1] to [5] above, characterized in that the outer circumferential wall surface of the cylindrical container is covered with a jacket, and a heating medium is supplied to the space formed between the jacket and the outer circumferential wall surface of the cylindrical container. [7] A drying apparatus for powders and granules according to any one of [1] to [6] above, characterized in that the cylindrical container is divided at any position in the axial direction, flanges are provided on the open end faces of each divided member, and the flanges are butted together and detachably connected with clamps or the like.

[0009] According to the powder and granular material drying apparatus of the present invention, the powder and granular material (material to be processed) is repeatedly circulated using a circulation path. This significantly extends the residence time of the powder and granular material (material to be processed). As a result, the powder and granular material can be dried more thoroughly. Furthermore, it is possible to produce processed products with less variation in drying. In addition, according to the powder and granular material drying apparatus of the present invention, the dried powder and granular material is returned through the circulation path to the vicinity of the perforated plate provided on the lower wall of the cylindrical container. With this configuration, the returned dried powder and granular material is mixed with new high-moisture untreated powder and granular material supplied from the introduction pipe. As a result, adhesion of the untreated powder and granular material to the perforated plates on the side walls and lower wall, which are the swirling mechanism, can be suppressed. Furthermore, the dispersibility of the untreated powder and granular material in the swirling upward airflow can be improved. Moreover, the drying apparatus of the present invention does not require an additional power source for the circulation of the powder and granular material. Therefore, the above effects can be achieved at a low cost. In addition, because the residence time of the powder and granular material dried in the internal space is increased, the size of the cylindrical container can be reduced. Therefore, the entire apparatus can be configured more compactly.

[0010] This is a longitudinal cross-sectional view of the apparatus according to the first embodiment of the present invention. This is an enlarged cross-sectional view of the portion along line A-A in Figure 1. This figure shows the apparatus according to the first embodiment of the present invention together with the necessary devices before and after it. This is an enlarged cross-sectional view of a perforated plate used in the apparatus of the present invention. This is an enlarged cross-sectional view of another perforated plate used in the apparatus of the present invention. This is a perspective view showing the lower end of a straight pipe member constituting a circulation path used in the apparatus of the present invention. This is a perspective view showing the upper ends of a guide member, a ring-shaped member, and a straight pipe member constituting a circulation path used in the apparatus of the present invention. This is a bottom view of the circulation path shown in Figure 7. This is a longitudinal cross-sectional view of the apparatus according to the second embodiment of the present invention. This figure shows the apparatus according to the second embodiment of the present invention together with the necessary devices before and after it. This is a longitudinal cross-sectional view of the apparatus according to the third embodiment of the present invention. This figure shows the apparatus according to the third embodiment of the present invention together with the necessary devices before and after it.

[0011] In the following, various embodiments of the powder and granular material drying apparatus according to the present invention will be described in detail with reference to the attached drawings.

[0012] Figures 1 to 3 show a first embodiment of the powder and granular material drying apparatus according to the present invention. In Figures 1 to 3, reference numeral 1 denotes a cylindrical container. The cylindrical container 1 has an internal space 2 in which any horizontal cross-section is concentric. The cylindrical container 1 is an upright container in which the axial direction is longer than the radial direction. Specifically, it is a cylindrical container with both end faces closed. However, the cylindrical container 1 is not limited to a cylindrical shape. It may be a truncated cone shape in which the diameter expands or contracts towards the bottom. It may also be a container with a shape in which the central part bulges like a beer barrel.

[0013] A perforated plate 3 is positioned at the bottom of the cylindrical container 1. The perforated plate 3 divides the internal space 2 of the cylindrical container 1 into a lower hot air chamber 2a and an upper drying chamber 2b. The perforated plate 3 is not limited to a flat plate. It may be a conical shape that is convex upwards or downwards in a concentric manner. In particular, if it is a conical shape that is convex downwards, it is preferable to connect a conduit to its lowest point. This conduit is for batch or continuous discharge of granular material that has accumulated without being carried by the airflow (not shown).

[0014] A heated gas introduction pipe 4 is connected to the side (or bottom) of the hot air chamber 2a formed at the bottom of the cylindrical container 1. Through the introduction pipe 4, air that has been purified by an air filter 50 located outside the machine and heated by an air heater 51 is sent to the hot air chamber 2a by a supply blower 52 (see Figure 3). In Figure 3, 53 is a supply pipe for a heating medium (such as steam), which supplies the heating medium to the air heater 51. Reference numeral 54 denotes a temperature control device. The temperature control device 54 is configured to control the opening and closing of a valve 57 provided on the supply pipe 53 based on the detection result of a temperature detector 56 provided in the middle of the heated gas supply pipe 55. The bottom surface 5 of the hot air chamber 2a does not necessarily have to be horizontal. The central part may be convex downwards or upwards. It may also be inclined in one direction as shown in the figure. In particular, when the bottom surface 5 is inclined, it is preferable because the cleaning water does not accumulate on the bottom surface 5 during cleaning and can be completely discharged through the drain pipe 58. Furthermore, by providing a handhole 59 on the side of the hot air chamber 2a as shown in Figure 3, inspection and cleaning of the hot air chamber 2a can be easily performed.

[0015] Multiple nozzles 6 are formed in the perforated plate 3 that constitutes the lower part of the cylindrical container 1. These nozzles 6 generate a swirling upward airflow when heated gas is introduced from the hot air chamber 2a to the drying chamber 2b via the perforated plate 3. The shape of each nozzle 6 is such that, for example as shown in Figure 4, a hole 7 is made in a flat plate, and the opening 8 faces in one direction substantially parallel to the plane of the flat plate. The upper part of the hole 7 is covered by a roof-like raised portion 9. As shown in Figure 2, multiple nozzles 6 are arranged in quarter-circular areas, with the openings 8 offset by 90° and facing the same direction (direction of the arrow in the figure). As a result, each opening 8 is positioned facing in one direction in the substantially circumferential direction on the concentric circles of the cylindrical container 1. Note that the nozzles 6 may also have a shape with the roof-like raised portion 9 facing downward, as shown in Figure 5. Alternatively, they may be long slit-shaped nozzles. Furthermore, the nozzle 6 may be positioned within a range of angles that is more finely divided than the range shown in Figure 2, such that the openings 8 face in the same direction.

[0016] A perforated plate 10 is provided on the inner circumferential wall surface of the container 1 located directly above the perforated plate 3. Multiple nozzles 6 are formed on the perforated plate 10 with a constant width around its entire circumference. These nozzles 6 have a structure similar to that shown in Figure 4 or Figure 5, and may be slit-shaped. As shown in Figure 2, the openings 8 of the nozzles 6 of the perforated plate 10 are regularly arranged so as to face one side in the tangential direction of the container 1. Therefore, the heated gas supplied into the drying chamber 2b via the perforated plate 10 flows in the same direction as the swirling airflow formed by the perforated plate 3 below. As a result, a nearly horizontal swirling airflow is formed in the drying chamber 2b. It is desirable that the lower circumferential surface of the perforated plate 10 be as close as possible to the perforated plate 3. Also, the joint between the perforated plate 10 and the perforated plate 3 does not need to be a right angle. An appropriate curvature or angle may be given to this corner. Furthermore, it is preferable to provide nozzles 6 at this corner as well, configured to blow out heated gas. This configuration prevents powder and granular material from adhering to and accumulating in the corners. Furthermore, the axial width of the perforated plate 10 is set to a size that sufficiently covers the upper end of the connection portion of the powder and granular material introduction pipe 13, which will be described later.

[0017] As shown in Figures 1 and 2, the outer circumference of the perforated plate 10, which constitutes the lower inner circumferential wall surface of the cylindrical container 1, is completely covered by the container 11 over its entire circumference and width. A hot air chamber 11a is formed between the container 11 and the perforated plate 10. A heated gas introduction pipe 12 is connected to the side of the hot air chamber 11a. As shown in Figure 3, air that has been purified by the air filter 50 and heated by the air heater 51 is supplied to the hot air chamber 11a via the introduction pipe 12 by the blowing action of the supply blower 52. In Figure 2, the heated gas introduction pipe 12 is connected perpendicular to the wall surface of the container 11. However, the introduction pipe 12 may also be connected from the direction in which the opening 8 of the nozzle 6 faces, that is, in a substantially tangential direction in the same rotational direction as the swirling upward airflow formed inside the cylindrical container 1. In this case, the ejection of heated gas into the drying chamber 2b is performed more smoothly. For similar reasons, it is preferable that the introduction pipe 4 for introducing heated gas into the hot air chamber 2a is connected from a substantially tangential direction with the same rotational direction as the swirling upward airflow inside the cylindrical container 1.

[0018] As shown in Figures 1 and 2, an introduction pipe 13 is connected to the side of the container 11 that covers the perforated plate 10. The introduction pipe 13 penetrates the container 11 and the perforated plate 10 inside it, supplying moist powder (material to be processed) into the drying chamber 2b. As shown in Figure 3, a powder / granular material quantitative feeder 60, such as a screw conveyor, is connected to the introduction pipe 13. It is preferable that the powder / granular material quantitative feeder 60 has a sealed structure to prevent heated gas in the drying chamber 2b from leaking to the outside through the introduction pipe 13, and to prevent outside air from flowing back into the drying chamber 2b. It is also desirable that a pressure balance is maintained inside the machine between the supply blower 52 and the exhaust blower 63, which will be described later.

[0019] A discharge pipe 14 for powder and heated gas is connected to the top side wall of the cylindrical container 1. The discharge pipe 14 is connected in a tangential direction in the same rotational direction as the swirling upward airflow formed inside the cylindrical container 1. As shown in Figure 3, the discharge pipe 14 is connected to an exhaust blower 63 via a powder separator 61 such as a cyclone and piping 62 located outside the machine. Note that the discharge pipe 14 does not necessarily have to be connected from the tangential direction. For example, it may be configured to be connected from the upper side in the central axis direction at the top (upper end face) of the cylindrical container 1.

[0020] A circulation passage 15 is provided between the perforated plate 3, which forms the lower wall of the cylindrical container 1, and the connection point of the discharge pipe 14 for the powder and heated gas, for circulating the powder within the cylindrical container 1. One open end 15a of the circulation passage 15 is located below the connection point of the discharge pipe 14, along the inner circumferential wall surface of the cylindrical container 1. The other open end 15b is located near the center of the perforated plate 3. This circulation passage 15 utilizes the swirling airflow within the cylindrical container 1, the inertial force associated with the swirling motion of the powder, and the pressure difference and gravity between the inside and outside of the cylindrical container 1 to return the powder from the top to the bottom of the cylindrical container 1. It is not necessary for the entire circulation passage 15 to be located inside the cylindrical container 1. Part of the passage may be located outside the container. However, one opening 15a must be located along the inner circumferential wall surface of the cylindrical container 1, and the other opening 15b must be located near the center of the perforated plate 3.

[0021] The circulation path 15 consists of a straight pipe member 16 arranged along the axis of the cylindrical container 1 and a guide member 17 connected to its upper end. In the embodiment shown in Figure 1, a ring-shaped member 18 is further provided directly above the guide member 17.

[0022] The straight pipe member 16 is a passage for returning the powdered material from the upper part of the cylindrical container 1 to the vicinity of the perforated plate 3, which is the lower wall. This straight pipe member 16 has a length from the installation position of the ring-shaped member 18 that blocks the powdered material to the perforated plate 3, which is the lower wall, and is arranged along the axis of the cylindrical container 1. By arranging the straight pipe member 16, which is the main passage of the circulation path 15, along the axis in this way, turbulence in the swirling upward airflow formed inside the cylindrical container 1 can be minimized. The upper end of the straight pipe member 16 is connected to the outlet (not shown) of the guide member 17, which will be described later, and the lower end is fixed to the perforated plate 3, which is the lower wall of the cylindrical container 1. In addition, as shown in Figure 6, a plurality (at least three, preferably four or more) of openings (outlets) 19 are formed in the lower side wall of the straight pipe member 16. These openings 19 constitute the other open end 15b of the circulation path 15. The shape of the openings 19 is not limited to the rectangle shown, but may be a semicircle or a semiellipse, etc. Furthermore, the lower end surface of the straight pipe member 16 is preferably a convex cone 20, from the viewpoint of preventing the accumulation of powder and granules. This powder and granule accumulation prevention configuration can also be achieved by installing the cone member in the center of the perforated plate 3 to which the lower end of the straight pipe member 16 is fixed. Alternatively, if the lower end surface of the straight pipe member 16 is not closed, the lower end side wall may be cut out in a rectangular, semicircular, or semi-elliptical shape to form an opening 19, and the tip of the remaining part may be fixed to the perforated plate 3, which is the lower wall.

[0023] The guide member 17, connected to the upper end of the straight pipe member 16, is a member for capturing the powder and granular material that swirls upward along the inner circumferential wall surface of the cylindrical container 1 and guiding it to the straight pipe member 16. The inlet 21 of the guide member 17 is located below the connection point of the discharge pipe 14 for the powder and granular material and heated gas, and is positioned along the inner circumferential wall surface of the cylindrical container 1. The inlet 21 opens in a direction opposite to the swirling upward airflow formed inside the cylindrical container 1, and this inlet 21 constitutes one of the open ends 15a of the circulation path 15. On the other hand, the outlet of the guide member 17 is connected to the upper end of the straight pipe member 16, as described above. As shown in Figures 7 and 8, the guide member 17 can be a hollow member having a rectangular inlet and passage, which is curved so as to be convex in the direction of the swirling airflow inside the cylindrical container 1. The shape of the inlet and passage may also be triangular, trapezoidal, or arc-shaped. The angle that the inlet 21 of the guide member 17 makes with respect to the inner circumferential wall surface of the cylindrical container 1 is preferably 90 degrees (normal direction) with respect to the tangential direction. However, this angle may be in the range of ±45 degrees, or even ±60 degrees. The number of guide members 17 connected to the straight pipe member 16 is not limited to one, but may be two or more as shown in the figures. When multiple guide members 17 are provided, it is preferable to arrange them in point-symmetrical positions as shown in Figures 7 and 8. Furthermore, it is desirable to provide a partition plate 22 inside the straight pipe member 16 so that the airflow and powder / granular material guided to the straight pipe member 16 after passing through each guide member 17 do not collide. In addition, although not shown in the figures, adjustment means such as louvers can be provided at the inlet 21 to adjust the amount of powder / granular material captured at the inlet 21 of the guide member 17.

[0024] In the embodiment shown in Figure 1, a ring-shaped member 18 is provided directly above the guide member 17. The ring-shaped member 18 prevents the granular material that has risen along the inner circumferential wall surface of the cylindrical container 1, accompanied by the swirling updraft, from being discharged to the outside from the discharge section 14, and instead causes it to remain in place. This allows the granular material to be efficiently captured at the inlet 21 of the guide member 17. The outer diameter of the ring-shaped member 18 is the same as the inner diameter of the horizontal cross-section of the cylindrical container 1 at the installation position. On the other hand, the inner diameter may be configured such that multiple ring-shaped members with different inner diameters are prepared and used as appropriate, depending on the average particle size of the granular material and the target moisture content (degree of dryness). Furthermore, welding is preferred as a method of fixing the ring-shaped member 18 to the cylindrical container 1, as it can suppress the adhesion of granular material. However, attachment by bolts, nuts, or other methods is also acceptable.

[0025] For the straight pipe member 16, guide member 17, and ring-shaped member 18 that constitute the circulation path 15, it is preferable to use metal materials such as stainless steel, carbon steel, or aluminum, which have excellent corrosion resistance, or plastics such as PTFE (polytetrafluoroethylene), or non-metallic materials such as ceramics, which have excellent heat resistance and chemical resistance. In particular, it is desirable to use materials that have been treated on the surface (e.g., Gemini processing, PTFE coating, multi-stage blasting) in order to reduce or prevent the adhesion of powders and granules.

[0026] The outer circumferential wall surface of the cylindrical container 1, which is equipped with a circulation path 15 (i.e., a straight pipe member 16, a guide member 17, and a ring-shaped member 18), is covered with a jacket 23, as shown in Figure 1. A space 24 is formed between the jacket 23 and the outer circumferential wall surface, and it is preferable to continuously supply a heating medium such as hot water or heated steam to this space 24 via a pipe 25 or pipe 26 and discharge it through the other pipe 26 or pipe 25. By heating the cylindrical container 1 from the outside in this way, conductive heat transfer by the heating medium occurs on the wall surface of the drying chamber 2b, and the powdered material can be dried efficiently. In addition, the effect of keeping at least the wall surface of the drying chamber 2b warm can be obtained.

[0027] Furthermore, as shown in Figure 3, the cylindrical container 1 is divided into a drying chamber 2b and a hot air chamber 2a at the position of the perforated plate 3. The drying chamber 2b is also divided directly above the perforated plate 10 and directly below the connection point of the discharge pipe 14. If necessary, the intermediate section may also be divided at approximately equal lengths in the axial direction. Each divided member is unitized by covering its outer circumference with a jacket 23, and a flange is provided on the open end face of each unit. It is preferable to butt these flanges together and connect them detachably with a clamp or the like, consisting of a pair of semicircular rings having recesses that extend almost the entire length in the inner circumferential direction. This configuration makes it easy to assemble and disassemble the device and allows for complete cleaning of the inside of the container. It is also possible to change the configuration of the circulation path 15 as necessary. For example, the ring-shaped member 18 can be replaced to adjust the degree of drying, or the straight pipe member 16 can be changed to change the circulation distance. Furthermore, it is possible to shorten or lengthen the length of the drying chamber 2b.

[0028] Next, a drying process for powders and granules using the drying apparatus of the present invention having the above configuration will be described in detail.

[0029] First, the supply blower 52 is activated to supply air, which has been purified by the air filter 50 and heated by the air heater 51, to the hot air chambers 2a and 11a, respectively, via the inlet pipes 4 and 12. This causes heated gas to be injected into the drying chamber 2b from the perforated plates 3 and 10. Simultaneously, the exhaust blower 63 is activated to draw in and exhaust the same amount of heated gas supplied from the drying chamber 2b to the hot air chambers 2a and 11a via the discharge pipe 14, the powder separator 61, and the piping 62. Furthermore, hot water at a predetermined temperature is continuously supplied via the pipe 26 to the space 24 formed between the outer periphery wall of the drying chamber 2b and the jacket 23, thereby heating the wall of the drying chamber 2b. The amount and ratio of heated gas injected from the perforated plates 3 and 10 can be controlled by valves 64 and 65 located in front of the inlet pipes 4 and 12, and valve 66 located in the middle of the piping 62.

[0030] Once the temperature inside the drying chamber 2b reaches a predetermined value, and the swirling upward airflow formed by the injection of heated gas from the perforated plates 3 and 10, and the circulating airflow through the circulation path 15 (straight pipe member 16, guide member 17, ring-shaped member 18) stabilize, the quantitative feeder 60 is activated. The powder and granular material are then quantitatively supplied into the drying chamber 2b from the introduction pipe 13.

[0031] The granular material supplied into the drying chamber 2b is forcibly dispersed by heated gas sprayed from the perforated plates 3 and 10, and rises on the swirling upward airflow formed within the drying chamber 2b. At this time, the granular material immediately after being supplied into the drying chamber 2b has a high moisture content and is prone to adhering to the inner circumferential wall surface of the container (the surface of the perforated plates 3 and 10). However, since heated gas is continuously sprayed from the perforated plates 3 and 10, this adhesion is effectively prevented. In addition, in the drying apparatus of the present invention, the granular material that has already been supplied and returned to the vicinity of the center of the perforated plate 3 via the circulation path 15 is mixed with the newly supplied untreated granular material with a high moisture content from the introduction pipe 13. This further suppresses adhesion to the inner circumferential wall surface and improves the dispersibility of the untreated granular material with a high moisture content in the swirling upward airflow.

[0032] When granular material is carried by a swirling updraft, it remains swirling within a nearly identical horizontal plane while it is wet and dense, due to the large effects of gravity and centrifugal force from the swirling updraft. During this time, drying progresses due to the thermal energy supplied by the heated gas and conductive heat transfer from the inner circumferential wall surface heated by the heating medium. As drying progresses and the granular material becomes lighter, the effects of gravity and centrifugal force decrease, and since new granular material is continuously supplied from the inlet pipe 13, the granular material moves upward, swirling and accompanied by the updraft.

[0033] The powdered material that rises inside the cylindrical container 1 on the swirling updraft is partially blocked by a ring-shaped member 18 located below the connection point of the discharge pipe 14 for the powdered material and heated gas. This blocks the material, separating it into two parts: some that remain in place, and others that pass through the central opening and continue to rise. This sorting phenomenon occurs because wet, high-density powdered material tends to rise along the inner circumferential wall of the cylindrical container 1 due to the large centrifugal force exerted by gravity and the swirling updraft. As a result, this wet powdered material is blocked by the ring-shaped member 18. On the other hand, dry, low-density powdered material is carried along by the updraft, passes through the central opening of the ring-shaped member 18, and moves further upward. In other words, the powdered material is automatically sorted by the ring-shaped member 18 according to its degree of dryness.

[0034] The granular material (that is not sufficiently dry) that is blocked by the ring-shaped member 18 and remains in place is captured by a guide member 17 located directly below the ring-shaped member 18. This guide member 17 is positioned along the inner circumferential wall surface of the cylindrical container 1 and has an inlet 21 that opens in a direction opposite to the swirling updraft formed inside the cylindrical container 1. The captured granular material is introduced through the guide member 17 into a straight pipe member 16 arranged along the axis of the cylindrical container 1. After that, it is returned to the vicinity of the center of the perforated plate 3, which is the lower wall of the cylindrical container 1, through an opening 19 provided at the lower end of the straight pipe member 16. This returned granular material is mixed with new untreated granular material supplied from the introduction pipe 13 and undergoes another drying process. Meanwhile, the granular material (that is sufficiently dry) that rises through the central opening of the ring-shaped member 18 is discharged outside the device through the upper discharge pipe 14, separated from the airflow in the granular material separator 61, and then recovered as dried granular material (processed product).

[0035] Next, an apparatus according to a second embodiment of the present invention will be described with reference to Figures 9 and 10. Components common to the first embodiment are denoted by the same reference numerals in Figures 9 and 10.

[0036] In the apparatus according to the second embodiment, as shown in Figure 9, the side wall of the cylindrical container 1 located below the discharge pipe 14 is formed by a perforated plate 30. This perforated plate 30 is equipped with nozzles 6 or elongated slits, similar to the perforated plate shown in Figure 4 or Figure 5. The openings 8 of the nozzles 6 are arranged in multiple locations so as to be regularly oriented in one tangential direction of the container 1, similar to the case of the perforated plate 10. The entire circumference of the perforated plate 30 is covered by the container 31, forming a hot air chamber 31a between the container 31 and the perforated plate 30. Furthermore, a heated gas introduction pipe 32 is connected to the side of this hot air chamber 31a. Through this introduction pipe 32, as shown in Figure 10, air that has been purified by an air filter 50 and heated by an air heater 51 is supplied by a supply blower 52. One open end 15a of the circulation path 15 (i.e., the inlet 21 of the guide member 17) is open in the portion along the inner circumferential wall surface of the cylindrical container 1 formed by the perforated plate 30. The other components are the same as those of the apparatus in the first embodiment. It is preferable that the heated gas introduction pipe 32 is connected to the container 31 from a substantially tangential direction in the same rotational direction as the swirling upward airflow formed inside the cylindrical container 1, similar to the introduction pipes 4 and 12 in the first embodiment.

[0037] In the apparatus with the above configuration, the granular material supplied into the drying chamber 2b via the introduction pipe 13 is forcibly dispersed by the heated gas sprayed from the perforated plates 3 and 10, similar to the first embodiment, and rises on the swirling upward airflow formed in the drying chamber 2b. The granular material dries due to the thermal energy of the heated gas and conductive heat transfer from the inner circumferential wall surface heated by the heating medium. As the granular material becomes lighter after drying, the effects of gravity and centrifugal force weaken, and new granular material is continuously supplied from the introduction pipe 13, causing it to move upward while swirling and moving towards the center, until it reaches the position where the perforated plate 30 is provided.

[0038] At the location where the perforated plate 30 is provided, heated gas is ejected from the perforated plate 30 into the drying chamber 2b via the introduction pipe 32. This creates an airflow that swirls rapidly in the circumferential direction along the perforated plate 30, i.e., an "air ring." This air ring entrains the granular material rising while swirling, retaining it in place, and also allows the dried, lighter granular material to pass through the central opening. In other words, it performs the same function as the ring-shaped member 18 in the first embodiment. Furthermore, this air ring also increases the local pressure at the location where it is formed.

[0039] The granular material that is caught in the air ring and remains there (granular material that has been classified as not sufficiently dry) is captured by a guide member 17 having an inlet 21 that opens along the inner circumferential wall surface of the cylindrical container 1, which is made up of a porous plate 30 forming the air ring. This captured granular material is introduced through the guide member 17 into a straight pipe member 16 arranged along the axis of the cylindrical container 1, and returned to the vicinity of the center of the porous plate 3, which is the lower wall of the cylindrical container 1, through an opening 19 provided at the lower end of the straight pipe member 16. The granular material returned to the vicinity of the center of the porous plate 3 is mixed with new untreated granular material supplied from the introduction pipe 13 and undergoes the drying process described above again. Meanwhile, the granular material that passes through the central opening of the air ring and rises (sufficiently dried granular material) is discharged outside the device through a discharge pipe 14 provided above, and after being separated from the airflow in the granular material separator 61, is recovered as dried granular material (processed product).

[0040] In the drying apparatus according to the second embodiment, the air ring formed inside the cylindrical container 1 performs the same function as the ring-shaped member 18 in the first embodiment. Therefore, it is no longer necessary to provide the ring-shaped member that was required in the first embodiment. Furthermore, the air ring formed inside the cylindrical container 1 not only blocks the rising granular material, but also applies centrifugal force to the granular material through high-speed swirling, causing it to collect and accumulate on the inner circumferential wall side of the cylindrical container 1. In addition, it also increases the pressure in the area where the air ring is formed, thereby improving the efficiency of capturing granular material at one of the opening ends 15a of the circulation path 15 (inlet 21 of the guide member 17). As a result, the amount of granular material circulated inside the cylindrical container 1 can be increased. Moreover, in this apparatus, the flow velocity and central opening diameter of the formed air ring can be easily adjusted by controlling the amount of heated gas ejected from the perforated plate 30. Specifically, by adjusting the airflow by opening and closing the valve 67 located in front of the introduction pipe 32 shown in Figure 10, it becomes possible to freely control the behavior of the powder or granular material, such as by letting it remain in place or by having it carried along by the rising airflow, according to the target moisture content (degree of dryness) of the powder or granular material.

[0041] Next, an apparatus according to a third embodiment of the present invention will be described with reference to Figures 11 and 12. In this embodiment as well, the same components as in the first embodiment are denoted by the same reference numerals in Figures 11 and 12.

[0042] The apparatus according to the third embodiment has a configuration in which a concentric drying chamber (hereinafter referred to as the "enlarged drying chamber 40") is formed as part of the drying chamber 2b below the position where one open end 15a of the circulation path 15 (i.e., the inlet 21 of the guide member 17) opens, with a horizontal cross-section larger than that of the other parts. The other parts have the same configuration as in the first embodiment.

[0043] Specifically, as shown in Figure 11, the expanded drying chamber 40 is formed by connecting a cylindrical member 41 with a larger inner diameter to a part of the cylindrical container 1 via truncated conical members 42 and 43.

[0044] In this apparatus as well, the outer peripheral wall surface of the enlarged drying chamber 40 is covered with a jacket 44, and a heating medium such as warm water or heating steam is continuously supplied to a space 45 formed between the jacket 44 and the outer peripheral wall surface through a pipe 46 or 47 and discharged from the pipe 47 or 46. Also, the cylindrical container 1 can be divided at the upper and lower portions of the enlarged drying chamber 40, and if necessary, the portions of the other drying chamber 2b can also be divided in substantially the same length in the axial direction. By providing flanges on the open end surfaces of the divided members to unitize them and making them easily joined by means of a clamp or the like, the apparatus can be easily assembled, disassembled, and cleaned as in the first embodiment. The cross-sectional area ratio of the enlarged drying chamber 40 is preferably in the range of 1.1 to 3.0 times, more preferably in the range of 1.1 to 2.0 times, that of the cross-sectional area of the other drying chamber 2b.

[0045] In the apparatus having the above configuration, in the portion of the enlarged drying chamber 40, the upward velocity of the swirling upward airflow rapidly decreases. Therefore, the granular material that has risen in the cylindrical container 1 stays while swirling in substantially the same horizontal plane in the portion of the enlarged drying chamber 40. This retained granular material is efficiently dried by the thermal energy brought in by the heating gas and further by the conductive heat transfer from the heating medium supplied to the space 45 on the outer peripheral wall surface of the enlarged drying chamber 40. Then, the granular material that has become lighter as drying progresses receives less centrifugal force from the swirling upward airflow, and swirls upward while moving toward the center and passes through the enlarged drying chamber 40.

[0046] The granular material that has passed through the enlarged drying chamber 40 and ascended within the cylindrical container 1 is classified by the ring-shaped member 18 that constitutes the aforementioned circulation path 15 and is provided below the connection portion of the discharge pipe 14 for the granular material and the heating gas. At this time, the still wet and high-density granular material is captured at the inlet 21 of the guiding member 17 provided directly below the ring-shaped member 18 and is guided to the straight pipe member 16 arranged along the axial center of the cylindrical container 1. Thereafter, it is returned from the opening 19 provided at the lower end of the straight pipe member 16 to the vicinity of the center of the porous plate 3 which is the lower wall of the cylindrical container 1. The granular material returned onto the porous plate 3 undergoes the above drying operation again, and the dried granular material with a reduced density is entrained by the upward airflow, passes through the central opening of the ring-shaped member 18, and is further discharged outside the apparatus through the discharge pipe 14 provided above it. The discharged granular material is separated from the airflow by the granular material separator 61 and recovered as dried granular material (processed product).

[0047] In the drying apparatus according to the third embodiment, an enlarged drying chamber 40 is formed in the middle of the drying chamber 2b. Thereby, the granular material can undergo a more effective drying process within the enlarged drying chamber 40. Further, this effect, in combination with the configuration provided with the circulation path 15 (the straight pipe member 16, the guiding member 17, and the ring-shaped member 18), enables further progress in the drying of the granular material and production of processed products with little variation in the drying state.

[0048] As described above, various embodiments of the drying apparatus for granular materials according to the present invention have been explained, but the present invention is not limited to these embodiments. A person skilled in the art can make various changes, improvements, or substitutions to the above embodiments. It is clear that forms with such changes or improvements are also included in the technical scope of the present invention based on the description in the claims.

[0049] The most distinctive feature of the present invention is that one open end 15a (the inlet 21 of the guide member 17) opens below the connection point of the discharge pipe 14 for the powder and heated gas and along the inner circumferential wall surface of the cylindrical container 1, and the other open end 15b (the opening 19 of the straight pipe member 16) opens near the center of the perforated plate 3 that forms the lower wall of the cylindrical container 1, and a powder circulation path 15 (straight pipe member 16 and guide member 17) is provided connecting these two ends. With this configuration, the drying apparatus of the present invention can repeat drying while circulating the powder (material to be processed), so the residence time in the internal space is greatly extended and drying can be further advanced. As a result, a homogeneous processed product with less uneven drying can be obtained. Furthermore, by returning the dried powder to near the center of the perforated plate 3, which is the lower wall, via the circulation path 15, it is mixed with new untreated powder with a high moisture content supplied from the powder introduction pipe 13. This prevents untreated granular material from adhering to the perforated plates 3 and 10 on the bottom and sides, improving the dispersibility of untreated granular material in the swirling upward airflow. Furthermore, because the drying apparatus of the present invention increases the residence time of granular material in the internal space, the size of the cylindrical container 1 can be reduced while maintaining equivalent drying performance, thereby reducing the overall installation volume of the apparatus.

[0050] The granular materials that can be processed by the drying apparatus of the present invention are extremely diverse, including various inorganic substances, organic substances, metals, polymers, and more. Furthermore, if the granular materials to be processed contain various organic solvents, or if there is a risk of ignition or explosion due to the physical properties of the granular materials, an inert gas such as nitrogen gas may be used as the heating gas instead of air.

[0051] 1: Cylindrical container, 2: Internal space, 2a: Hot air chamber, 2b: Drying chamber, 3: Perforated plate, 4: Inlet pipe for heated gas, 5: Bottom surface of hot air chamber, 6: Outlet, 7: Hole, 8: Opening, 9: Roof-like raised section, 10: Perforated plate, 11: Container, 11a: Hot air chamber, 12: Inlet pipe for heated gas, 13: Inlet pipe for powder and granular material, 14: Outlet pipe for powder and granular material and heated gas, 15: Circulation path, 15a: One open end, 15b: The other open end, 16: Straight pipe member, 17: Guide member, 18: Ring-shaped member, 19: Opening (outlet), 20: Conical section, 21: Inlet, 22: Cut plate, 23: Jacket, 24: Space, 25, 26: Tube 30: Perforated plate, 31: Container, 31a: Hot air chamber, 32: Inlet pipe for heated gas, 40: Enlarged drying chamber, 41: Cylindrical member with large inner diameter, 42, 43: Truncated conical member, 44: Jacket, 45: Space, 46, 47: Pipe, 50: Air filter, 51: Air heater, 52: Supply blower, 53: Supply pipe for heating medium (water vapor, etc.), 54: Temperature control device, 55: Supply pipe, 56: Temperature detection, 57: Valve, 58: Drain pipe, 59: Handhole, 60: Quantitative feeder for powders and granules, 61: Powder and granule separator, 62: Piping, 63: Exhaust blower, 64, 65, 66, 67: Valve

Claims

1. A drying apparatus for powders and granules comprising a cylindrical container having a concentric internal space with a horizontal cross-section of any height, an introduction pipe for powders and a heating gas introduction pipe connected to the lower part of the cylindrical container, a swirling mechanism that causes the heating gas introduced from the introduction pipe to swirl upward within the cylindrical container, and discharge pipes for powders and heating gas connected to the upper part of the cylindrical container, wherein the lower side wall of the cylindrical container is made of a perforated plate with a plurality of nozzles formed therein, with the openings facing one direction tangential to the cylindrical container, the periphery of the perforated plate is covered by a container, and the heating gas introduction pipe is connected to the container, and the lower wall of the cylindrical container is made of a perforated plate with a plurality of nozzles formed therein, with the openings facing one direction substantially circumferentially on a concentric circle with the cylindrical container, the area below the perforated plate is covered by a container, and the heating gas introduction pipe is also connected to the container, thereby constituting the heating gas swirling mechanism, A drying apparatus for powders and granules, characterized by having a circulation path for powders and granules, where one open end is located below the connection point of the discharge pipe for the powders and heated gas and along the inner circumferential wall surface of the cylindrical container, and the other open end is located near the center of the perforated plate forming the lower wall of the cylindrical container.

2. The drying apparatus for powders and granules according to claim 1, characterized in that a ring-shaped member is provided in a portion of the cylindrical container located directly above the opening of one end of the circulation path, which blocks the powders and granules that have swirled upward along the inner circumferential wall surface of the cylindrical container.

3. The drying apparatus for powders and granules according to claim 1, characterized in that the side wall of a cylindrical container located below the connection portion of the discharge pipes for the powders and granules and heated gas is made of a porous plate having a plurality of nozzles arranged such that the opening faces the same direction as the direction of rotation of the swirling upward airflow formed inside the cylindrical container by the swirling mechanism, the periphery of the porous plate is covered with a container, and the introduction pipe for the heated gas is also connected to the container, thereby forming an air ring at that position that blocks the powders and granules that have swirled upward along the inner circumferential wall surface of the cylindrical container, and one end of the circulation path is opened along the inner circumferential wall surface of the cylindrical container at the portion where the air ring is formed.

4. The drying apparatus for powders and granules according to claim 1, characterized in that the circulation path comprises a straight pipe member arranged along the axis of a cylindrical container and a guide member connected to the upper end of the straight pipe member, the inlet of the guide member opens in a direction opposite to the swirling upward airflow formed inside the cylindrical container at a point below the connection of the discharge pipes for the powders and heated gas and along the inner circumferential wall surface of the cylindrical container, and the lower end of the straight pipe member opens directly above the perforated plate constituting the lower wall of the cylindrical container.

5. The drying apparatus for powders and granules according to claim 1, characterized in that the cylindrical container has an internal space in which the horizontal cross-section is enlarged in the middle of its axial direction compared to other parts and is concentric, and one end of the circulation path is opened in a part located above the enlarged portion and below the connection part of the discharge pipe for the powders and heated gas.

6. A drying apparatus for powders and granules according to any one of claims 1 to 5, characterized in that the outer circumferential wall surface of the cylindrical container is covered with a jacket, and a heating medium is supplied to the space formed between the jacket and the outer circumferential wall surface of the cylindrical container.

7. A drying apparatus for powders and granules according to any one of claims 1 to 5, characterized in that the cylindrical container is divided at any position in the axial direction, flanges are provided on the open end faces of each divided member, and the flanges are butted together and detachably joined with clamps or the like.

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