Powder material processing apparatus and drying method

Abstract

To provide a powder material processing apparatus and a drying method, capable of efficiently drying a powder material.SOLUTION: In a heating part 2 (heating step), a powder material is heated, and the heated powder material is supplied to a vacuum drying part 3. In the vacuum drying part 3 (vacuum drying step), the powder material is dried under a reduced-pressure environment without increasing the heat quantity of the powder material. In the reduced-pressure environment, since the partial pressure of water vapor in air is low, when the powder material heated in the heating part 2 is placed in the reduced-pressure environment, a boiling point of moisture contained in the powder material decreases, and the moisture contained in the powder material is rapidly vaporized. Therefore, if the powder material is sufficiently heated in the heating part 2, the powder material can be satisfactorily dried in the vacuum drying part 3 without increasing the heat quantity of the powder material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a powder or granular material processing apparatus and a drying method. [Background technology]

[0002] For example, in the manufacturing process of plastic products, a drying process is performed to remove moisture from powdered or granular plastic material before the powdered or granular plastic material is fed into a molding machine.

[0003] Conventionally, devices used for drying processes include hot air heating dryers and reduced pressure heat transfer dryers. In hot air heating dryers, a heater generates high-temperature hot air, which is supplied into a container containing powder or granular material, and moisture from the powder or granular material is removed by the hot air passing through the powder or granular material. In reduced pressure heat transfer dryers, a heater heats the wall of the container containing the powder or granular material. While the pressure inside the container containing the powder or granular material is reduced, the powder or granular material is heated by heat transfer from the wall of the container, and moisture evaporates from the powder or granular material.

[0004] However, both the hot air heating dryer and the reduced pressure heat transfer dryer have the problem of large energy consumption because the heater is used until the powder or granular material is dried.

[0005] One drying device proposed is one that combines a hot air heating dryer and a reduced-pressure heat transfer dryer (see, for example, Patent Document 1). This device is provided with a preheating hopper and a reduced-pressure drying hopper. A heater generates high-temperature hot air, which is supplied into the preheating hopper containing powder or granular material, and the powder or granular material is heated by the hot air. A jacket is provided around the reduced-pressure drying hopper. The high-temperature hot air is supplied to the jacket, heating the wall surface of the reduced-pressure drying hopper. The powder or granular material heated in the preheating hopper is supplied to the reduced-pressure drying hopper, and while the pressure inside the reduced-pressure drying hopper is reduced, the powder or granular material is heated by heat transfer from the wall surface of the reduced-pressure drying hopper. This dries the powder or granular material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-79841 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in this type of device, because both the preheating hopper and the vacuum drying hopper must be heated with hot air, it is not possible to significantly reduce energy consumption compared to conventional hot air heating dryers and vacuum heat transfer dryers. Furthermore, when using hot air for heating, it takes time for the preheating hopper and the vacuum drying hopper to heat up.

[0008] An object of the present invention is to provide a powder or granular material processing apparatus and a drying method that can efficiently dry powder or granular material. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a powder or granular material processing apparatus according to one aspect of the present invention includes a heating section that heats the powder or granular material, a reduced-pressure drying section that dries the powder or granular material in a reduced-pressure environment without increasing the heat content of the powder or granular material, and a supply section that supplies the powder or granular material heated in the heating section to the reduced-pressure drying section.

[0010] According to this configuration, the powder or grain is heated in the heating section and the heated powder or grain is supplied to the reduced-pressure drying section. The reduced-pressure drying section dries the powder or grain in a reduced-pressure environment without increasing the amount of heat the powder or grain receives. Because the partial pressure of water vapor in the air is low in a reduced-pressure environment, the boiling point of the water contained in the powder or grain is lowered by placing the powder or grain heated in the heating section in a reduced-pressure environment, and the water contained in the powder or grain is quickly vaporized. Therefore, if the powder or grain is sufficiently heated in the heating section, the powder or grain can be satisfactorily dried in the reduced-pressure drying section without increasing the amount of heat the powder or grain receives.

[0011] Therefore, in comparison with a configuration in which the calorific value of the powder or granule is increased by heating in the reduced pressure drying section, the amount of energy consumed can be reduced and the powder or granule can be dried efficiently.

[0012] The heating section may include a heating container for containing powdered or granular material, a heater for heating the powdered or granular material contained in the heating container, and a stirring mechanism for stirring the powdered or granular material contained in the heating container.

[0013] In this configuration, the powder and granules can be stirred while being heated in the heating container, which prevents the powder and granules from welding to each other or to the wall of the heating container, and allows the powder and granules to be heated evenly.

[0014] The heater is preferably an infrared heater.

[0015] The infrared rays emitted from the infrared heater can quickly raise the temperature of the powder or granular material.

[0016] The stirring mechanism may include an agitator that is rotatably provided around a rotation axis within the heating container, and a rotation mechanism that rotates the agitator.

[0017] The heating container may be a heating drum having a cylindrical peripheral wall and rotatable about the center line of the peripheral wall, and the stirring mechanism may include a rotation mechanism that rotates the heating drum.

[0018] The reduced pressure drying section may include a reduced pressure drying container that accommodates powder or granular material, and a decompression mechanism that reduces the pressure inside the reduced pressure drying container.

[0019] The powder or granular material processing apparatus may further include an air supply mechanism that supplies air into the reduced pressure drying container for discharging the powder or granular material from the reduced pressure drying container.

[0020] In this configuration, air can be supplied into the reduced pressure drying container, and the supply of air allows the powder or granular material to be efficiently discharged from the reduced pressure drying container.

[0021] The heating vessel is preferably disposed above the vacuum drying vessel.

[0022] This allows the powder or granules to be supplied from the heating container to the reduced-pressure drying container under their own weight. Compared to a configuration in which the powder or granules are supplied from the heating container to the reduced-pressure drying container by pneumatic transport, this configuration can suppress a decrease in the temperature of the powder or granules when they are supplied from the heating container to the reduced-pressure drying container, allowing the powder or granules to be dried more efficiently.

[0023] The reduced pressure drying unit may further include a container heater for heating the reduced pressure drying container.

[0024] The container heater is not used to increase the heat content of the powder or granular material after it has been supplied into the vacuum drying container, but is used to warm the vacuum drying container when the powder or granular material processing apparatus is started up. That is, when the powder or granular material processing apparatus is started up, the vacuum drying container is cooled to approximately room temperature. If powder or granular material is supplied into the vacuum drying container in this state, the temperature of the powder or granular material will drop, which could result in insufficient drying of the powder or granular material. Therefore, when the powder or granular material processing apparatus is started up, the container heater is used to warm the vacuum drying container to a temperature close to that of normal operation before powder or granular material is supplied into the vacuum drying container. This prevents insufficient drying due to the vacuum drying container being too cold.

[0025] A method for drying powder or granular material according to another aspect of the present invention includes a heating step of heating the powder or granular material in a heating container, a supplying step of supplying the powder or granular material from the heating container to a reduced-pressure drying container, and a reduced-pressure drying step of reducing the pressure inside the reduced-pressure drying container after the supplying step, and drying the powder or granular material in a reduced-pressure environment without increasing the heat content of the powder or granular material.

[0026] According to this method, powder or grain is heated in a heating container and the heated powder or grain is supplied from the heating container to a reduced-pressure drying container. The reduced-pressure drying container is then placed in a reduced-pressure environment, where the powder or grain is dried without increasing its heat output. In a reduced-pressure environment, the partial pressure of water vapor in the air is low. Therefore, by placing the powder or grain heated in the heating section in a reduced-pressure environment, the boiling point of the water contained in the powder or grain is lowered, and the water contained in the powder or grain is quickly vaporized. Therefore, if the powder or grain is sufficiently heated in the heating step, the powder or grain can be satisfactorily dried in the reduced-pressure drying step without increasing its heat output.

[0027] In the heating step, the powder or granule is preferably heated using an infrared heater.

[0028] The infrared rays emitted from the infrared heater can quickly raise the temperature of the powder or granular material. [Effects of the Invention]

[0029] According to the present invention, powder or granular material can be dried efficiently. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram illustrating the configuration of a powder / granular material processing apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view illustrating the internal configuration of the heating hopper, taken along a vertical plane perpendicular to the side wall of the heating hopper. [Figure 3] FIG. 2 is a cross-sectional view illustrating the internal configuration of the heating hopper, taken along a vertical plane parallel to the side wall of the heating hopper. [Figure 4] FIG. 2 is a process diagram showing the flow of powder and granular material drying processing. [Figure 5] 10 is a flowchart showing the flow of a reduced pressure drying hopper heating process. [Figure 6] FIG. 10 is a diagram illustrating the configuration of a powder or granular material processing apparatus according to another embodiment of the present invention. [Figure 7A]FIG. 2 is a cross-sectional view illustrating the configuration of the heating drum, showing the state during agitation of powder and granular material. [Figure 7B] FIG. 2 is a cross-sectional view diagrammatically showing the configuration of the heating drum, illustrating the state when powder or granular material is being discharged. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0032] <Powder and granular material processing equipment> FIG. 1 is a diagram illustrating the configuration of a powder or granular material processing apparatus 1 according to one embodiment of the present invention.

[0033] The powder and granular material processing apparatus 1 is included in a plastic product manufacturing facility and is a device that dries powder and granular material such as plastic pellets, which are raw materials for plastic products. The powder and granular material processing apparatus 1 includes a heating section 2 that heats the powder and granular material, a reduced-pressure drying section 3 that dries the powder and granular material in a reduced-pressure environment without increasing the calorific value (thermal energy) of the powder and granular material, and a supply section 4 that supplies the powder and granular material heated in the heating section 2 to the reduced-pressure drying section 3.

[0034] The heating unit 2 employs an infrared heating hopper system. That is, the heating unit 2 includes a heating hopper 11 that accommodates powder and granular material, and an infrared heater 12 that heats the powder and granular material accommodated in the heating hopper 11.

[0035] 2 and 3 are cross-sectional views illustrating the internal structure of the heating hopper 11. FIG.

[0036] The heating hopper 11 has, for example, a rectangular prism-shaped upper portion and a trapezoidal prism-shaped lower portion that tapers downward. The heating hopper 11 has a pair of opposing side walls 13, 14 that are parallel to each other at both the upper and lower portions. As shown in Figure 1, a rectangular discharge port 15 is formed at the lower end of the heating hopper 11.

[0037] 2 is a cross-sectional view of the heating hopper 11 taken along a vertical plane perpendicular to the side walls 13 and 14, and FIG. 3 is a cross-sectional view of the heating hopper 11 taken along a vertical plane parallel to the side walls 13 and 14.

[0038] The infrared heater 12 is, for example, a cylindrical halogen heater, and is provided at the upper end of the heating hopper 11, straddling between the side walls 13 and 14 of the heating hopper 11, as shown in FIG.

[0039] A reflector plate 16 is provided within the heating hopper 11. As shown in Fig. 3, the reflector plate 16 has a flat horizontal portion 17 that is above the infrared heater 12 and extends parallel to the infrared heater 12 in the longitudinal direction of the infrared heater 12, and inclined portions 18 and 19 that extend obliquely from each edge of the horizontal portion 17 extending in the longitudinal direction to a position below the lower end of the infrared heater 12. Infrared rays radiated from the top of the infrared heater 12 to its surroundings are reflected downward by the inner surfaces of the horizontal portion 17 and the inclined portions 18 and 19.

[0040] An agitator 21 is provided at the bottom of the heating hopper 11. The agitator 21 includes a shaft 22 and multiple blades 23. The shaft 22 extends in the same direction as the longitudinal direction of the infrared heater 12. Both ends of the shaft 22 penetrate the side walls 13, 14 of the heating hopper 11 and are rotatably supported by the side walls 13, 14 via bearings. A motor 24 is coupled to one end of the shaft 22 (for example, the end on the side wall 14 side) outside the heating hopper 11. The multiple blades 23 are arranged at intervals in the axial direction of the shaft 22 and extend radially from the shaft 22.

[0041] As shown in FIG. 1, the reduced pressure drying section 3 includes a reduced pressure drying hopper 31 that accommodates powder and granular material, and a decompression mechanism 32 that reduces the pressure inside the reduced pressure drying hopper 31.

[0042] The reduced pressure drying hopper 31 has, for example, a cylindrical upper portion and a conical or truncated conical lower portion that tapers downward from the upper portion. A discharge port 33 is formed at the lower end of the reduced pressure drying hopper 31. The upper end of a discharge pipe 34 is connected to the discharge port 33. A discharge valve 35 that opens and closes the discharge pipe 34 is interposed in the discharge pipe 34. The upper surface of the reduced pressure drying hopper 31 is closed by a top plate 36. In addition, to prevent the reduced pressure drying hopper 31 from being cooled by the outside air, a heat insulating material 38 is wrapped around the outer periphery of the side wall 37 of the reduced pressure drying hopper 31. Furthermore, a planar rubber heater 39 is attached to a portion of the side wall 37.

[0043] The pressure reduction mechanism 32 includes a pressure reduction line 41, a pressure reduction pump 42, and a pressure reduction filter 43. A pressure reduction port 44 is formed in the top plate 36 of the vacuum drying hopper 31, and one end of the pressure reduction line 41 is connected to the pressure reduction port 44. The pressure reduction pump 42 is connected to the pressure reduction line 41. The pressure reduction filter 43 is interposed midway along the pressure reduction line 41, between the pressure reduction port 44 and the pressure reduction pump 42, in order to prevent powder and granular materials from being released through the pressure reduction line 41.

[0044] The heating hopper 11 is disposed above the reduced pressure drying hopper 31 and is supported on the top plate 36 of the reduced pressure drying hopper 31 via a bracket 51 .

[0045] The supply unit 4 is equipped with a supply pipe 52. The supply pipe 52 is formed in a rectangular cylindrical shape corresponding to the shape of the discharge port 15 of the heating hopper 11, and extends in the vertical direction between the heating hopper 11 and the reduced-pressure drying hopper 31. The upper end of the supply pipe 52 is connected to the periphery of the discharge port 15 of the heating hopper 11. The lower end of the supply pipe 52 is an open end that is inclined when viewed from the opposing direction of the side walls 13, 14 of the heating hopper 11. In addition, the lower end of the supply pipe 52 is disposed at a position spaced above a supply port 53 formed in the top plate 36 of the reduced-pressure drying hopper 31, and faces the supply port 53 in the vertical direction.

[0046] The supply unit 4 also includes a damper 54 and an actuator 55. The damper 54 is plate-shaped and is provided so as to be displaceable between an open position where it is spaced apart from the lower end of the supply pipe 52 and a closed position where it abuts against the lower end of the supply pipe 52. The actuator 55 is supported by the bracket 51. The actuator 55 is, for example, an air cylinder, and displaces the damper 54 between the open position and the closed position.

[0047] The powder and granular material processing device 1 further includes a loader hopper 5 for supplying the (undried) powder and granular material to be processed to the heating section 2, and an air supply mechanism 6 for supplying air to promote drying and to release the vacuum when discharging the powder and granular material.

[0048] The loader hopper 5 is disposed above the heating hopper 11. The loader hopper 5 has, for example, a cylindrical upper portion and a conical or truncated conical lower portion that tapers downward from the upper portion. A discharge port 61 is formed at the lower end of the loader hopper 5. One end of a discharge pipe 62 is connected to the discharge port 61. The discharge pipe 62 extends downward from the discharge port 61. As shown in FIG. 2 , the heating hopper 11 is provided with a receiving section 63 that extends outward from the upper end of the side wall 13, and the other end (lower end) of the discharge pipe 62 is connected to the receiving section 63. The interior of the receiving section 63 communicates with the interior of the heating hopper 11 via a receiving port (not shown) formed in the side wall 13. A discharge valve 64 that opens and closes the discharge pipe 62 is provided in the discharge pipe 62.

[0049] One end of a transport pipe 66 is connected to a side wall 65 of the loader hopper 5. The other end of the transport pipe 66 is connected to a suction pipe 67. Undried powder and granular material is stored in a material tank (not shown), and the suction pipe 67 is disposed within the powder and granular material.

[0050] One end of a suction pipe 69 is connected to the top plate 68 of the loader hopper 5. The other end of the suction pipe 69 is connected to the suction port of a transport blower (not shown). Although not shown, a dust collecting cyclone or the like is installed midway along the suction pipe 69 to collect powder and granular materials sucked into the suction pipe 69 from inside the loader hopper 5.

[0051] The air supply mechanism 6 includes, for example, three air supply pipes 71, 72, and 73. One end of the air supply pipe 71 is connected to the upper end of the side wall 13 of the heating hopper 11. An auxiliary valve 74 is installed midway through the air supply pipe 71 to inject air that causes convection within the heating hopper 11 in order to uniformly heat the powder and granular material in the heating section 2. One end of the air supply pipe 72 is connected to the upper end of the side wall 37 of the reduced-pressure drying hopper 31. A vacuum breaker valve 75 is installed midway through the air supply pipe 72 to open and close the air supply pipe 72. One end of the air supply pipe 73 is connected midway through the discharge pipe 34, between the discharge port 33 and the discharge valve 35. The other ends of the air supply pipes 71, 72, and 73 are connected to a membrane air dryer 76. An air injection valve 77 is installed in the pipe that takes air into the membrane air dryer 76.

[0052] The powder or granular material processing apparatus 1 also includes a control unit 7 for controlling each part of the powder or granular material processing apparatus 1. The control unit 7 includes a microcomputer (microcontroller). The microcomputer has a built-in CPU and memory. The memory includes, for example, non-volatile memory that allows data to be rewritten, such as flash memory or E2PROM, and volatile memory, such as DRAM (Dynamic Random Access Memory). The non-volatile memory stores programs for controlling each part of the powder or granular material processing apparatus 1. The CPU executes the programs stored in the non-volatile memory and uses the volatile memory as a work area when executing the programs. The memory also stores various data necessary for controlling each part.

[0053] <Drying process for powder and granular materials> FIG. 4 is a process diagram showing the flow of the powder / granular material drying process.

[0054] In the process of drying powder or granular material, a heating step (step S1), a supplying step (step S2), and a reduced pressure drying step (step S3) are carried out in this order.

[0055] Prior to the heating step (step S1), the transport blower is operated to supply the powder or granular material to be processed from the material tank to the loader hopper 5. When the transport blower is operated, negative pressure is generated in the suction pipe 69. This negative pressure causes the powder or granular material in the material tank to be sucked into the transport pipe 66 through the suction pipe 67, and the powder or granular material is then supplied from the transport pipe 66 into the loader hopper 5. While the powder or granular material is being supplied to the loader hopper 5, the discharge valve 64 is closed. When the supply of the powder or granular material to the loader hopper 5 is completed, the discharge valve 64 is opened, and the powder or granular material is supplied from the loader hopper 5 through the discharge pipe 62 and the receiving section 63 into the heating hopper 11 of the heating section 2. At this time, the damper 54 is in the closed position, and the auxiliary valve 74, vacuum break valve 75, and air injection valve 77 are closed.

[0056] In the heating step (step S1), the auxiliary valve 74 is opened to inject a small amount of air into the heating hopper 11. Meanwhile, the infrared heater 12 is turned on. The motor 24, which is the rotational drive source for the agitator 21, is also operated. As a result, the agitator 21 rotates in the heating hopper 11, and while the powder and granules are being agitated by the agitator 21, infrared rays emitted from the infrared heater 12 are absorbed by the powder and granules, and the thermal energy of the powder and granules increases due to the absorption of the infrared rays. As a result, the temperature of the powder and granules in the heating hopper 11 rises evenly and quickly. After a predetermined heating time has elapsed since the start of the heating step (turning on the infrared heater 12), the infrared heater 12 is turned off, the motor 24 is stopped, and the heating step of heating the powder and granules is completed. The heating time is set, for example, depending on the type and amount of powder and granules, the target temperature, and the like.

[0057] In the supply step (step S2), the actuator 55 of the supply unit 4 is actuated to displace the damper 54 from the closed position to the open position. As a result, the powder or granular material heated in the heating step is supplied from the heating hopper 11 through the supply pipe 52 and the supply port 53 into the reduced-pressure drying hopper 31 of the reduced-pressure drying unit 3. The discharge valve 35 is closed, and the powder or granular material supplied into the reduced-pressure drying hopper 31 is stored at the bottom of the reduced-pressure drying hopper 31. When a predetermined supply time has elapsed since the start of the supply step (actuator 55 was actuated), the actuator 55 is stopped, the damper 54 is actuated from the open position to the closed position, and the supply step of supplying the powder or granular material from the heating unit 2 to the reduced-pressure drying unit 3 is completed. The supply time is set, for example, depending on the type and amount of the powder or granular material.

[0058] In the reduced-pressure drying process (step S3), the vacuum pump 42 is operated while the discharge valve 35 remains closed. The vacuum breaker valve 75 and air injection valve 77 remain closed since the powder and granules were supplied to the loader hopper 5. Therefore, when the vacuum pump 42 is operated, the air in the reduced-pressure drying hopper 31 is sucked into the vacuum line 41, reducing the pressure inside the reduced-pressure drying hopper 31. The reduced pressure inside the reduced-pressure drying hopper 31 reduces the partial pressure of water vapor in the air inside the hopper 31, lowering the boiling point of the moisture contained in the powder and granules, thereby quickly evaporating the moisture from the powder and granules. After a predetermined reduced-pressure drying time has elapsed since the start of the reduced-pressure drying process (operation of the reduced-pressure pump 42), the operation of the reduced-pressure pump 42 is stopped, and the reduced-pressure drying process, in which the powder and granules are dried under reduced pressure, is completed. The reduced-pressure drying time is set, for example, depending on the type and amount of powder and granules. During the reduced-pressure drying process, the rubber heater 39 remains off, preventing the heat generation from increasing.

[0059] When the reduced-pressure drying process is completed, the discharge valve 35 is opened. In addition, the vacuum break valve 75 and the air injection valve 77 are opened. When the vacuum break valve 75 and the air injection valve 77 are opened, air (outside air) is taken into the membrane air dryer 76, where it is dehumidified to become dry air, and the dry air flows through the air supply pipes 71, 72, and 73 into the heating hopper 11, the reduced-pressure drying hopper 31, and the discharge pipe 34, respectively. As a result, the powder and granular material in the reduced-pressure drying hopper 31 is discharged from the reduced-pressure drying hopper 31 through the discharge pipe 34 and is pneumatically transported, for example, through a transport pipe to which the discharge pipe 34 is connected, to a destination hopper located above the injection molding machine. Furthermore, even if powder or granular material adheres to the inner surfaces of the heating hopper 11, the reduced pressure drying hopper 31, and the discharge pipe 34 due to electrostatic adhesion, the adhering powder or granular material is effectively purged by supplying dry air to the inside of the heating hopper 11, the reduced pressure drying hopper 31, and the discharge pipe 34.

[0060] <Decompression drying hopper heating treatment> FIG. 5 is a flowchart showing the flow of the reduced pressure drying hopper heating process.

[0061] In the powder / granular material processing apparatus 1, a reduced pressure drying hopper heating process is performed by the control unit 7. The reduced pressure drying hopper heating process is a process in which the reduced pressure drying hopper 31 is heated using the rubber heater 39.

[0062] The reduced pressure drying hopper heating process is performed when the power supply to the powder or granular material processing apparatus 1 is turned on and the powder or granular material processing apparatus 1 is started. In the reduced pressure drying hopper heating process, it is determined whether the start of the powder or granular material processing apparatus 1 is an initial start (step S11). For example, if the powder or granular material processing apparatus 1 is started after a certain time has passed since the end of the drying process without any new drying process being performed, the start is determined to be an initial start of the powder or granular material processing apparatus 1.

[0063] If the start-up of the powder or granular material processing apparatus 1 is an initial start-up (YES in step S11), the rubber heater 39 is turned on (step S12). By turning on the rubber heater 39, heat is conducted from the rubber heater 39 to the reduced pressure drying hopper 31, and the reduced pressure drying hopper 31 rises in temperature.

[0064] Thereafter, it is determined whether or not the heating of the reduced pressure drying hopper 31 has been completed (step S13). For example, when a predetermined heating time has elapsed since the rubber heater 39 was turned on, the heating of the reduced pressure drying hopper 31 is completed.

[0065] The rubber heater 39 remains on until the heating of the reduced pressure drying hopper 31 is completed. Then, when the heating of the reduced pressure drying hopper 31 is completed (YES in step S13), the rubber heater 39 is turned off (step S14), and the reduced pressure drying hopper heating process is ended.

[0066] On the other hand, if the start of the powder or granular material processing apparatus 1 is not the initial start (NO in step S11), the rubber heater 39 is not turned on, and the reduced pressure drying hopper heating process is ended with the rubber heater 39 remaining off.

[0067] <Action and effect> As described above, the powder or granules are heated in the heating section 2 (heating step), and the heated powder or granules are supplied to the reduced-pressure drying section 3. Then, in the reduced-pressure drying section 3 (reduced-pressure drying step), the powder or granules are dried in a reduced-pressure environment without increasing the amount of heat the powder or granules receive. In a reduced-pressure environment, the partial pressure of water vapor in the air is low, and so by placing the powder or granules heated in the heating section 2 in a reduced-pressure environment, the boiling point of the water contained in the powder or granules is lowered, and the water contained in the powder or granules quickly evaporates. Therefore, if the powder or granules are sufficiently heated in the heating section 2, the powder or granules can be satisfactorily dried in the reduced-pressure drying section 3 without increasing the amount of heat the powder or granules receive.

[0068] Therefore, in the reduced pressure drying section 3, the amount of energy consumed can be reduced compared to a configuration in which the calorific value of the powder or granule is increased by heating, and the powder or granule can be dried efficiently.

[0069] The heating unit 2 includes a heating hopper 11 that accommodates powdered or granular material, an infrared heater 12 that heats the powdered or granular material accommodated in the heating hopper 11, and an agitator 21 and motor 24 that agitate the powdered or granular material accommodated in the heating hopper 11. This allows the powdered or granular material to be heated and agitated in the heating hopper 11. Agitating the powdered or granular material prevents the powdered or granular material from welding to each other or to the wall of the heating hopper 11, and also allows the powdered or granular material to be heated evenly. In addition, the infrared rays emitted from the infrared heater 12 can quickly raise the temperature of the powdered or granular material.

[0070] The reduced pressure drying section 3 includes a reduced pressure drying hopper 31 that accommodates powder or granular material, and a decompression mechanism 32 that reduces the pressure inside the reduced pressure drying hopper 31. The powder or granular material processing apparatus 1 also includes an air supply mechanism 6 that can supply dry air into the reduced pressure drying hopper 31. By supplying dry air into the reduced pressure drying hopper 31, the powder or granular material can be smoothly discharged from the reduced pressure drying hopper 31.

[0071] The heating hopper 11 is disposed above the reduced pressure drying hopper 31. This allows the powder or granular material to be supplied by its own weight from the heating hopper 11 to the reduced pressure drying hopper 31. Compared to a configuration in which the powder or granular material is supplied from the heating hopper 11 to the reduced pressure drying hopper 31 by pneumatic transport, this configuration can suppress a drop in the temperature of the powder or granular material when it is supplied from the heating hopper 11 to the reduced pressure drying hopper 31, thereby allowing the powder or granular material to be dried more efficiently.

[0072] The reduced-pressure drying unit 3 includes a rubber heater 39 that heats the reduced-pressure drying hopper 31. The rubber heater 39 is not used to increase the heat content of the powder or granules after they are supplied into the reduced-pressure drying hopper 31, but rather to warm the reduced-pressure drying hopper 31 during initial startup of the powder or granule processing apparatus 1. Specifically, during initial startup of the powder or granule processing apparatus 1, the reduced-pressure drying hopper 31 is cooled to approximately room temperature. If powder or granules are supplied into the reduced-pressure drying hopper 31 in this state, the temperature of the powder or granules may drop, resulting in insufficient drying of the powder or granules. Therefore, during initial startup of the powder or granule processing apparatus 1, the rubber heater 39 is used to warm the reduced-pressure drying hopper 31 to a temperature close to that during normal operation before the powder or granules are supplied into the reduced-pressure drying hopper 31. This prevents insufficient drying due to the reduced pressure of the reduced-pressure drying hopper 31. Note that the rubber heater 39 may not necessarily be used depending on the required level of powder or granule drying processing.

[0073] <Other embodiments> Fig. 6 is a diagram illustrating the configuration of a powder or granular material processing apparatus 101 according to another embodiment of the present invention. In Fig. 6, parts corresponding to those shown in Fig. 1 are given the same reference numerals as those parts. In the following, the description of the parts given the same reference numerals will be omitted, and the configuration of the powder or granular material processing apparatus 101 will be described focusing on the differences from the configuration shown in Fig. 1.

[0074] 1, powder and granular material processing apparatus 101 is an apparatus for performing a process of drying powder and granular material such as plastic pellets. Powder and granular material processing apparatus 101 includes a heating section 102 that heats powder and granular material, and a supply section 104 that supplies the powder and granular material heated in heating section 102 to reduced-pressure drying section 3.

[0075] The heating unit 102 employs an infrared heating drum system, which includes a heating drum 111 that contains powder and granular material, and an infrared heater 112 that heats the powder and granular material contained in the heating drum 111.

[0076] 7A and 7B are cross-sectional views illustrating the configuration of the heating drum 111. FIG.

[0077] The heating drum 111 has a cylindrical peripheral wall 113 and is provided so as to be rotatable about the center line of the peripheral wall 113. The peripheral wall 113 is formed with rectangular discharge openings 114 that extend long in the direction of the center line of the peripheral wall 113, for example, at positions that are 180° symmetrical in the circumferential direction of the peripheral wall 113 (hereinafter simply referred to as the "circumferential direction").

[0078] Two dam plates 115 and two stirring plates 116 are provided inside the heating drum 111. The dam plates 115 extend from one circumferential edge 117 of each discharge port 114 and, when viewed from the direction of the center line of the peripheral wall 113, are inclined toward the other circumferential edge 118 of the discharge port 114 with respect to a line passing through the edge 117 and the center line of the peripheral wall 113. The stirring plates 116 are rectangular plates extending in the radial direction and in the direction of the center line of the peripheral wall 113 and are arranged between the two dam plates 115 in the circumferential direction, at positions 180° symmetrical in the circumferential direction, with a gap between them and the inner circumferential surface of the heating drum 111.

[0079] A discharge guide 119 is provided on the outer periphery of the heating drum 111. The discharge guide 119 extends from an edge 118 of each discharge opening 114, bends toward an edge 117, and extends along the outer periphery of the peripheral wall 113.

[0080] The infrared heater 112 is, for example, a halogen heater. A heater case 121 is provided inside the heating drum 111. The heater case 121 has a rectangular parallelepiped shape and extends along the center line of the peripheral wall 113. One surface of the heater case 121 facing downward is open, and the infrared heater 112 is held inside the heater case 121 and faces the inside of the heating drum 111 from the open surface of the heater case 121.

[0081] As shown in FIG. 6, the heating unit 102 is provided with a rotation mechanism 122 that rotates the heating drum 111, and a chute 123 that receives the powder or granular material discharged from the heating drum 111.

[0082] The rotation mechanism 122 includes a motor 124 as a rotation drive source.

[0083] The chute 123 is disposed below the heating drum 111. The upper surface of the chute 123 is open, and has a length that allows the leading edge of the discharge guide 119 to face the entire length of the chute 123 in the direction of the center line of the peripheral wall 113. The chute 123 is formed in the shape of a triangular prism that tapers downward. A discharge port 125 is formed at the lower end of the chute 123.

[0084] The supply section 104 includes a discharge branch pipe 131 , a transport pipe 132 , a transport destination hopper 133 , a supply pipe 134 and a supply valve 135 .

[0085] A branch pipe 136 is formed in the discharge branch pipe 131. The branch pipe 136 is connected to a discharge outlet 125 at the lower end of the chute 123. In addition, one end of a transport pipe 132 is connected to the discharge branch pipe 131.

[0086] The destination hopper 133 is disposed above the reduced pressure drying hopper 31, and has a cylindrical upper portion and a conical or truncated conical lower portion that tapers downward and continues from the upper portion. A discharge port 137 is formed at the lower end of the destination hopper 133. One end of a supply pipe 134 is connected to the discharge port 137. The other end of the supply pipe 134 is connected to the top plate 36 of the reduced pressure drying hopper 31. A supply valve 135 is provided midway along the supply pipe 134.

[0087] The other end of the transport pipe 132 is connected to a side wall 138 of a destination hopper 133 .

[0088] The supply unit 104 also includes a transport suction air switching valve 141 , a suction pipe 142 , a negative pressure pipe 143 , and a transport blower 144 .

[0089] The transport suction air switching valve 141 has a first input port 145, a second input port 146, and an output port 147. The transport suction air switching valve 141 is provided with valve bodies that individually open and close the first input port 145 and the second input port 146. Depending on the positions of the valve bodies, the transport suction air switching valve 141 can be switched between a first transport position in which the second input port 146 is closed and the first input port 145 is opened, thereby connecting the first input port 145 to the output port 147 within the valve body, and a second transport position in which the first input port 145 is closed and the second input port 146 is opened, thereby connecting the second input port 146 to the output port 147 within the valve body.

[0090] One end of the suction pipe 142 is connected to the top plate 151 of the transport destination hopper 133. The other end of the suction pipe 142 is connected to the second input port 146 of the transport suction air switching valve 141.

[0091] One end of the negative pressure pipe 143 is connected to the output port 147 of the transport suction air switching valve 141. The other end of the negative pressure pipe 143 is connected to the suction port of the transport blower 144. In the middle of the negative pressure pipe 143, a dust collecting cyclone 152 and a transport filter 153 are installed in this order from the transport suction air switching valve 141 side in order to collect powder and granular materials flowing through the negative pressure pipe 143.

[0092] Further, a branch pipe 154 is formed in the discharge branch pipe 131. One end of an air supply pipe 155 is connected to the branch pipe 154. The other end of the air supply pipe 155 is connected to the outlet of the transport blower 144.

[0093] The loader hopper 5 is disposed above the heating drum 111. One end of a discharge pipe 62 is connected to a discharge port 61 at the lower end of the loader hopper 5, and the other end (lower end) of the discharge pipe 62 is connected to a receiving port 157 formed in an end wall 156 that forms one end surface of the heating drum 111. One end of a suction pipe 69 is connected to a top plate 68 of the loader hopper 5, and the other end of the suction pipe 69 is connected to a first input port 145 of the transport suction air switching valve 141.

[0094] In the powder / granular material processing apparatus 101, prior to the heating step (step S1 in FIG. 4 ), when the powder / granular material to be processed is supplied from the material tank to the loader hopper 5, the transport / suction air switching valve 141 is set to the first transport position. When the transport blower 144 is operated, negative pressure is generated in the vacuum pipe 143, the valve body of the transport / suction air switching valve 141, and the suction pipe 69. This negative pressure causes the powder / granular material in the material tank to be sucked into the transport pipe 66 through the suction pipe 67, and the powder / granular material is supplied from the transport pipe 66 to the loader hopper 5. While the powder / granular material is being supplied to the loader hopper 5, the discharge valve 64 is closed. When the supply of the powder / granular material to the loader hopper 5 is completed, the discharge valve 64 is opened, and the powder / granular material is supplied from the loader hopper 5 through the discharge pipe 62 and the receiving port 157 into the heating drum 111 of the heating section 102.

[0095] In the heating step (step S2 in FIG. 4), the infrared heater 112 is turned on. The motor 124 of the rotation mechanism 122 is also activated. The activation of the motor 124 starts the rotation of the heating drum 111. At this time, the driving force of the motor 124 rotates the heating drum 111 so that the edge 117 of each discharge port 114 is located downstream in the rotation direction relative to the edge 118 opposite the edge 117 and the opposite edge 118 across the discharge port 114, as shown in FIG. 7A. The powder and granular material contained in the heating drum 111 is guided by the blocking plate 115 to pass over the discharge port 114 and is agitated by the agitator 116 without being discharged from the discharge port 114. While the powder and granular material is agitated by the agitator 21, the infrared rays emitted from the infrared heater 12 are absorbed by the powder and granular material, and the absorption of the infrared rays increases the thermal energy of the powder and granular material. As a result, the temperature of the powder and granular material in the heating hopper 11 is raised evenly and quickly.

[0096] When a predetermined heating time has elapsed since the start of the heating process (when the infrared heater 112 is turned on), the infrared heater 112 is turned off. Then, the rotation direction of the motor 124 is reversed, and the heating drum 111 is rotated by the driving force of the motor 124 so that the edge 118 of each discharge port 114 is downstream in the rotation direction from the edge 117 opposite the edge 117 across the discharge port 114, as shown in FIG. 7B. The powder or granular material contained in the heating drum 111 is blocked by the blocking plate 115 and discharged from the discharge port 114 while being guided by the discharge guide 119. The powder or granular material falling from the discharge guide 119 is received by the chute 123. When a predetermined time has elapsed since the rotation direction of the motor 124 was reversed, the motor 124 is stopped, and the heating process for heating the powder or granular material is completed.

[0097] The supply process (step S3 in FIG. 4) is started simultaneously with or during the start of discharge of the powdered or granular material from the heating drum 111. In the supply process, the supply valve 135 of the supply unit 104 is opened. In addition, the transport suction air switching valve 141 is set to the second transport position, and the transport blower 144 is operated. When the transport blower 144 is operated, negative pressure is generated in the negative pressure pipe 143, the valve box of the transport suction air switching valve 141, and the suction pipe 142. This negative pressure causes the powdered or granular material received in the chute 123 to be supplied into the destination hopper 133 through the discharge port 125 at the bottom of the chute 123, the discharge branch pipe 131, and the transport pipe 132. The powdered or granular material supplied into the destination hopper 133 is then supplied into the reduced-pressure drying hopper 31 through the discharge port 137 at the bottom of the destination hopper 133 and the supply pipe 134. When a predetermined supply time has elapsed since the start of the supply process (the operation of the transport blower 144), the operation of the transport blower 144 is stopped, the supply valve 135 is closed, and the supply process of supplying the powder or granular material from the heating section 102 to the reduced-pressure drying section 3 is completed. The supply time is set, for example, depending on the type and amount of the powder or granular material.

[0098] <Action and effect> The configuration of the powder or granular material processing apparatus 101 can also achieve the same effects as the configuration of the powder or granular material processing apparatus 1 shown in FIG.

[0099] However, in the configuration of the heating section 102, the discharge outlet 114 of the heating drum 111 is always open, so it may take longer for the temperature of the powder or granular material to rise than in the configuration of the heating section 2 of the powder or granular material processing apparatus 1.

[0100] <Modification> Although two embodiments of the present invention have been described above, the present invention can also be embodied in other forms.

[0101] For example, as the pressure in the vacuum drying hopper 31 decreases and the inside of the vacuum drying hopper 31 approaches a vacuum, the pressure in the vacuum drying hopper 31 will no longer decrease. If this state continues, the amount of air discharged from the vacuum drying hopper 31 to the vacuum line 41 will be small, and the water vapor in the vacuum drying hopper 31 will not be sufficiently discharged, resulting in a decrease in the drying efficiency of the powder or granular material. To prevent this, the air injection valve 77 of the air supply mechanism 6 may be opened intermittently to intermittently supply dry air from the air supply pipe 72 into the vacuum drying hopper 31. Alternatively, dry air may be injected continuously, as long as the amount is small enough to maintain the desired degree of vacuum.

[0102] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0103] 1,101: Powder and granular material processing equipment 2,102: Heating section 3: Reduced pressure drying section 4,104: Supply department 6: Air supply mechanism 11: Heating hopper (heating container) 12,112: Infrared heater 21: Agitator 24: Motor (rotation mechanism) 31: Vacuum drying hopper (vacuum drying container) 32: Pressure reduction mechanism 39: Rubber heater (container heater) 111: Heating drum 113: Peripheral wall 122: Rotation mechanism

Claims

1. a heating unit that heats the powder and granular material; a reduced-pressure drying unit that dries the powder or granular material in a reduced-pressure environment without increasing the heat quantity of the powder or granular material; a supply section that supplies the powder or granular material heated in the heating section to the reduced-pressure drying section.

2. The heating unit is a heating container for accommodating powder and granular material; a heater for heating the powder or granular material contained in the heating container; The powder / granular material processing apparatus according to claim 1 , further comprising: an agitation mechanism for agitating the powder / granular material contained in the heating container.

3. The powder / granular material processing apparatus according to claim 2 , wherein the heater is an infrared heater.

4. The stirring mechanism includes: an agitator rotatably provided around a rotation axis within the heating container; The powder / granular material processing apparatus according to claim 3 , further comprising: a rotation mechanism that rotates the agitator.

5. the heating container is a heating drum having a cylindrical peripheral wall and being rotatable around a center line of the peripheral wall, The powder / granular material processing apparatus according to claim 3 , wherein the stirring mechanism includes a rotation mechanism that rotates the heating drum.

6. The reduced pressure drying section a vacuum drying vessel for accommodating powder and granular material; The powder or granular material processing apparatus according to claim 2 , further comprising a decompression mechanism for decompressing the inside of the reduced-pressure drying container.

7. 7. The powder or granular material processing apparatus according to claim 6, further comprising an air supply mechanism that supplies air into said reduced-pressure drying container for discharging the powder or granular material from said reduced-pressure drying container.

8. The powder or granular material processing apparatus according to claim 6 , wherein the heating container is disposed above the reduced-pressure drying container.

9. The powder or granular material processing apparatus according to claim 6 , wherein the reduced pressure drying unit further includes a container heater for heating the reduced pressure drying container.

10. a heating step of heating the powder or granular material in a heating container; a supply step of supplying powder or granular material from the heating container to a reduced-pressure drying container; a reduced-pressure drying step of reducing the pressure inside the reduced-pressure drying container after the supplying step, and drying the powder or granule in a reduced-pressure environment without increasing the heat quantity of the powder or granule.

11. The drying method according to claim 10, wherein the heating step heats the powder or granules using an infrared heater.

Images