JP3677226B2 - Centrifugal dehydration dryer for resin pellets - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dehydration dryer that removes moisture from resin pellets cut and molded in water, and in particular, removes moisture adhering to resin pellets by dehydration and drying using centrifugal force. The present invention relates to a centrifugal dehydration dryer for resin pellets.
[0002]
[Prior art]
For example, the resin pellets are produced by an underwater cut pellet manufacturing apparatus 1 that cuts a resin that has been melt-kneaded and extruded into water from a forming die into a strand as shown in a schematic diagram in FIG. Manufactured. That is, in the underwater cut type pellet manufacturing apparatus 1, the synthetic resin raw material melted and kneaded by the rotary screw 3 of the kneading extruder 2 is fed from the molding die 4 provided at the tip of the kneading extruder 2 into the cooling water chamber 5. Extruded into strands of water. In connection with the forming die 4, an underwater cutting device 6 having a cutter knife 7 rotating on the surface of the forming die 4 and a drive motor 8 for driving the cutter knife 7 via a drive shaft 9 is provided. The strand-like molten resin extruded from the forming die 4 is cut into the resin pellets P by being cut by the cutter knife 7 in the water in the cooling water chamber 5.
[0003]
The cooling water chamber 5 of the underwater cutting device 6 is supplied with cooling water from the cooling water tank 10 through the filter 12 by the pumping action of the circulation pump 11. The produced resin pellets P are cooled by the cooling water, and are sent to the dehydrator 14 through the conveying line 13 using the cooling water as pellet conveying water. The resin pellets introduced into the dehydrator 14 may be partly attached resin masses, but such resin masses are separated by a dehydration screen 15 and can be transported to a cart 16 that can be carried out. It is thrown in. A large amount of pellet transport water that has passed through the dewatering screen 15 is returned from the drain port 17 of the dehydrator 14 into the cooling water tank 10.
[0004]
Since the resin pellets separated from the resin lump and the transport water by the dewatering screen 15 are attached with moisture, the resin pellets are usually sent from the pellet outlet 18 to the centrifugal dehydration dryer 20, and further in the centrifugal dehydration dryer 20. Dehydrated. FIG. 4 is a longitudinal sectional view showing an example of a conventional centrifugal dehydration dryer 20. Although details of the structure of the centrifugal dehydration dryer 20 will be described later, the resin pellets are guided to a pellet inlet 21 arranged at the lower part of the centrifugal dehydration dryer 20, and are then lifted up by rotating blades as will be described later. To be transported. At this time, water adhering to the pellet surface is spun off from the resin pellet by the action of centrifugal force. The resin pellets are also slightly dried by touching the airflow in the dehydration dryer 20 while being conveyed toward the top. The dehydrated resin pellets are guided from the upper pellet discharge port 22 to the vibration sieving machine 25 as the next process. In the vibration sieving machine 25, the resin pellets are classified according to size, and resin pellets having a size within a predetermined range are sent to a pellet silo (not shown) through an air feed line 26 including an air feed pipe and stored. .
[0005]
The cooling water transported by the resin pellets and separated by the dewatering screen 15 of the dehydrator 14 passes through the drain port 17, and the water separated by the centrifugal force in the centrifugal dehydration dryer 20 passes through the drain port 23, respectively. Return to 10. The cooling water returned to the tank 10 is sent to the underwater cutting device 6 by the circulation pump 11, is continuously automatically circulated, and is reused for cooling and transporting the resin pellets. Further, an exhaust duct 24 is provided at the upper part of the centrifugal dehydration dryer 20, and the moisture generated inside the centrifugal dehydration dryer 20 is sucked by a suction fan and discharged to the outside through the exhaust duct 24, so that the centrifugal dehydration drying is performed. The drying capacity of the machine 20 is improved. Also in the vibration sieving machine 25, the exhaust fan 27 is provided so that moisture generated inside the vibration sieving machine 25 is discharged to the outside through the exhaust duct 28.
[0006]
As shown in FIG. 4, the centrifugal dehydration dryer 20 has a structure in which a cylindrical outer cylinder 31 is vertically installed on a base 30. The drive motor 32 is also supported in a vertically placed state via a housing 33 attached to the upper part of the outer cylinder 31. A rotating body 34 that is rotationally driven by a driving motor 32 is disposed in the outer cylinder 31, and an output of the driving motor 32 is transmitted to a rotating shaft 36 of the rotating body 34 via a coupling 35. . The rotary shaft 36 is arranged in a vertically extending state, and is supported in a state in which the upper and lower ends are rotatable with respect to the outer cylinder 31 by bearings 37 and 37 and are regulated in the vertical direction.
[0007]
The rotating body 34 has a rotating body 38 attached to the rotating shaft 36, and a plurality of plate-like rotating blades 39 (a part of which is given a reference numeral) arranged on the outer peripheral surface of the rotating body 38. . Since each rotary blade 39 is attached at a rake angle with respect to the rotation direction, it has an action of picking up the fed pellets upward and transporting them. A cylindrical screen 40 is arranged inside the outer cylinder 31 and surrounding the rotary blade 39. The cylindrical screen 40 is supported by a plurality of stays 41 with respect to the outer cylinder 31 at the positions of the upper and lower end portions and the intermediate position. The mesh of the cylindrical screen 40 does not allow the resin pellets to pass through, but is set to a roughness that allows moisture to pass through. An annular space 42 formed between the rotating body 38 and the outer cylinder 31 includes an inner space 43 formed on the rotating body 38 side and an outer space 44 formed on the outer cylinder 31 side by the cylindrical screen 40. It is divided into The inner space 43 is connected to the pellet inlet 21 at the lower end, and is connected to the pellet outlet 22 at the upper end. The outer space 44 is connected to the drain outlet 23 at the lower end. The annular space 42 is sealed by the end walls at the top and bottom, except that the pellet inlet 21, the pellet outlet 22 and the drain 23 are provided.
[0008]
The resin pellets fed from the pellet loading port 21 are scraped up by the rotary blades 39 of the rotating body 34 driven by the drive motor 32, and move upward in the inner space 43 between the rotating body 38 and the cylindrical screen 40. And is guided from the pellet discharge port 22 provided at the upper end to the vibration sieving machine 25 which is the next step. The resin pellets collide with the rotary blades 39 and the cylindrical screen 40 during conveyance in the inner space 43, or the resin pellets collide with each other. To be separated. The separated water is scattered by passing through the cylindrical screen 40 by the action of centrifugal force, collected in the outer space 44, and returned to the tank 10 through the drain port 23.
[0009]
The drive motor 32 is usually an induction motor having a constant rotation speed of 4 poles or 6 poles, but a variable speed motor may be used. The drive motor 32 is attached to the upper part in the illustrated example, but may be attached to the lower part. Further, the belt may be driven by a V pulley. Power is supplied to the drive motor 32 through the power lead 45.
[0010]
In general, specifications such as the number of rotating blades 39 in the centrifugal dehydration dryer 20, the mounting angle, the rotational speed, the rotational radius, the height of the rotating body 34, etc. Although it is determined by the amount of water, the following measures are taken to promote the drying of the resin pellets. That is, when the dryness of the resin pellets is low (the water content is high), an exhaust duct 24 is connected to the upper part of the centrifugal dehydration dryer 20 and the pellet discharge port 22, and a suction fan is connected to the exhaust duct 24. Measures to arrange are taken. Moisture generated by drying the resin pellets in the centrifugal dehydration dryer 20 is sucked outside through the exhaust duct 24 by the suction fan. In order to improve the efficiency of dehydration and drying, drying air is blown into the centrifugal dehydration dryer 20 to increase the degree of drying. If the above modification is impossible, measures such as changing the number and angle of the rotating blades 39, the number of rotations, the diameter of the rotating body 34, and increasing the height of the rotating body 34 may be taken. Taken.
[0011]
[Problems to be solved by the invention]
However, the dewatering capacity of the conventional centrifugal dehydrator as described above mainly depends on the centrifugal force, and there is a limit to the efficient removal of moisture. Evaporation of water is only evaporation due to self-heating of the resin pellets themselves during transportation in the centrifugal dehydration dryer or contact with the internal airflow, and does not completely dry out the water adhering to the resin pellets. Even if the moisture in the centrifugal dehydration dryer is exhausted using a suction fan, the moisture discharge itself is effective, but it does not actively remove the water adhering to the resin pellets. In addition, blowing dry air into the centrifugal dehydration dryer is expensive due to large-scale modifications such as the need to incorporate a duct for blowing, resulting in the production cost of resin pellets. Will be raised.
[0012]
Therefore, in the centrifugal dehydration dryer for resin pellets that dehydrates and dries the resin pellets produced by the underwater cut method, in addition to dewatering the adhering moisture using centrifugal force, the inside of the centrifugal dehydration dryer is heated to a high temperature. Therefore, there is a problem to be solved in that the evaporation of water adhering to the resin pellet is promoted to efficiently remove the water from the resin pellet.
[0013]
The object of the present invention is to solve the above-mentioned problems and not only dehydrate by shaking off moisture using centrifugal force, but also evaporate moisture adhering to the resin pellets by raising the temperature inside the centrifugal dehydration dryer. For resin pellets that can improve the drying capacity and ensure the removal of moisture from the resin pellets at low cost and improve the reliability of the resin pellets as a product without major equipment remodeling It is to provide a centrifugal dehydration dryer.
[0014]
[Means for Solving the Problems]
A centrifugal dehydration dryer for resin pellets according to the present invention includes a rotating body having a plurality of rotating blades attached to the outer periphery to scrape up the resin pellets to which moisture has adhered, and a water passage through which the rotating blade is disposed outside the rotating body. consists a cylindrical screen but to allow passage of resin pellets is to prevent, from an induction heating means for directly heating the rotating body by inducing eddy currents in the rotating body. The rotating body is provided with a temperature sensor, and heating of the rotating body by the induction heating means is controlled based on the detected temperature detected by the temperature sensor and the set temperature set by the temperature setting device. Has been.
[0015]
According to this centrifugal dewatering dryer for resin pellets, when resin pellets cut in water are supplied to the space formed by the rotating body and the cylindrical screen, the resin pellets are attached to the outer periphery of the rotating body. and scooped up Ri by the plurality of rotating blades with a rake angle are. Since the resin pellets are blown outwardly is blocked by the cylindrical screen, only moisture adhering to the resin pellets, in a conventional manner and is discharged through the tubular screen by the action of centrifugal force. On the other hand, by induction heating means to induce eddy currents in the rotating body, the rotation body to the rotating body is Joule heat is generated by eddy currents becomes high, the rotation body around the heat conduction from the rotary member The temperature of the atmosphere increases and the humidity decreases. As a result, moisture adhering to the resin without being completely dehydrated, or touch the high temperature of the rotating body, or receive heat from the temperature rise resin pellets, and more will be or receives heat from the high temperature atmosphere Since evaporation is promoted, the drying capacity of the centrifugal dehydration dryer is improved. Furthermore, since the heating of the rotating body by the induction heating means is controlled based on the detected temperature of the rotating body and the set temperature, it becomes possible to prevent overheating of the rotating body, and the resin pellet The attached moisture will be evaporated more efficiently and effectively.
[0016]
Further, in this centrifugal dewatering dryer for resin pellets, the rotating body has a rotating body having a hollow inside, and the induction heating means can be an induction coil disposed inside the rotating body. . By doing so, the induction coil as the induction heating means is arranged inside the hollow rotary body, so that no space is required for the arrangement of the induction heating means, and the centrifugal dehydration dryer can be enlarged. Absent.
[0017]
Furthermore, in this centrifugal dewatering dryer for resin pellets, the rotary body is disposed around the fixed shaft so as to be concentric and rotatable with the fixed shaft, and the induction coil is disposed around an iron core attached to the fixed shaft. Further, it is possible to adopt a configuration in which a current is supplied to the induction coil through a power supply wire disposed on a fixed shaft. With such a configuration, the induction coil is arranged by winding the induction coil around the iron core attached to the fixed shaft and supplying the current to the induction coil through a power supply wire provided on the fixed shaft. And the power supply wiring can be made compact.
[0018]
This centrifugal dehydration dryer for resin pellets can be applied in place of the centrifugal dehydration dryer in the conventional underwater cut type resin production apparatus. For this purpose, it is preferable that the centrifugal pellet dewatering dryer for resin pellets has a vertically placed structure in which a rotating body rotates around a rotating shaft extending in the vertical direction. In addition, an outer cylinder is disposed outside the cylindrical screen, and the dehydrated water is collected and drained to the outside through a drain outlet provided on the lower side. A structure may be adopted in which resin pellets are put into the lower end of the dewatering cylinder, scraped up by a rotating blade, and dehydrated and dried resin pellets are discharged from the upper end.
[0019]
In this centrifugal dewatering dryer for resin pellets , the rotating body is further divided into a plurality of parts in the axial direction, and temperature sensors are provided for each section, and a set temperature is given for each section, and the induction overheating is performed. The control of the heating of the rotating body by the means can be performed for each section based on the detected temperature and the set temperature corresponding to the section . By doing so, the temperature of the rotating body can be controlled more finely.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a centrifugal dewatering dryer for resin pellets according to the present invention will be described below with reference to the accompanying drawings. 1 is a longitudinal sectional view showing an embodiment of a centrifugal dewatering dryer for resin pellets according to the present invention, and FIG. 2 is a sectional view taken along line AA of the centrifugal dewatering dryer for resin pellets shown in FIG. . In this embodiment, the same components as those used in the conventional centrifugal pellet dehydrator for resin pellets described in FIGS. 3 and 4 are the same as those in FIGS. 3 and 4. The description which overlaps is abbreviate | omitted.
[0021]
As shown in FIG. 1, this resin pellet centrifugal dehydration dryer (hereinafter abbreviated as “centrifugal dehydration dryer”) 50 includes a fixed shaft 51 fixed to a machine frame, and a fixed shaft 51. A rotating body 54 is provided around the fixed shaft 51 so as to be concentric and rotatable. The fixed shaft 51 includes an upper end portion 52a, a lower end portion 52b, and a cylindrical shaft portion 52c that connects both end portions 52a and 52b. The rotating body 54 includes a rotating body 55 having a hollow inside with the rotary blades 39 attached to the outer peripheral surface, an upper annular end wall 55a fixed integrally with the upper end and the lower end of the rotating body 55, and a lower side. An annular end wall 55b is provided, and both the annular end walls 55a and 55b are rotatably supported by the upper end portion 52a and the lower end portion 52b of the fixed shaft 51 through bearings 53 and 58, respectively. ing.
[0022]
The rotating body 54 also has a shaft end portion 56 extending upward from the upper annular end wall 55a. The shaft end portion 56 is rotatable by a bearing 57 with respect to the housing 33 integral with the outer cylinder 31. While being supported, the extreme end is connected to the drive motor 32 via the coupling 35. The lower annular end wall 55 b of the rotating body 54 is rotatably supported by a fixed shaft 51 integral with the outer cylinder 31 via a thrust bearing 58, and the load of the rotating body 54 is fixed via the thrust bearing 58. The shaft 51 is transmitted to the base 30.
[0023]
As is apparent from FIGS. 1 and 2, an iron core 60 is mounted on the outer periphery of the cylindrical shaft portion 52 c of the fixed shaft 51 in the hollow interior of the rotary body 55, and an induction coil 61 is disposed outside the iron core 60. Is arranged. In order to avoid the induction coil 61 from contacting the rotating body 54, an appropriate gap 62 is provided between the outer surface of the induction coil 61 and the inner surface of the rotating body 55 of the rotating body 54. The power supply wire 63 connected to the commercial power source extends through the lower end portion 52 b of the fixed shaft 51 and supplies power to the induction coil 61. The rotating body 55 is usually made of stainless steel because the pellets come into contact with it, but in any case, a magnetic material is used.
[0024]
When a high-frequency current is passed from the commercial power source to the induction coil 61 through the feeding wire 63, an alternating magnetic flux is generated around the induction coil 61 wound around the iron core 60, and the rotating body existing in a region through which the high-frequency alternating magnetic flux passes. An eddy current is generated at 55 so as to resist the change of the alternating magnetic field. As a result, Joule heat is generated in the rotating body 55 by eddy current, and the rotating body 55 is directly heated. The heat generated in the rotating body 55 is also transferred to the rotating blades 39, and the entire rotating body 54 becomes high temperature. If the alternating magnetic field reaches the rotating blade 39, the rotating blade 39 itself is also directly heated. The atmosphere in the inner space 43 between the cylindrical screen 40 and the rotating body 55 also increases in temperature due to heat conduction from the rotating body 54 that has become high temperature and friction caused by the stirring action of the rotating blades 39. Decreases (dryness increases). The moisture adhering to the resin pellets is not only centrifugally dehydrated, but also promotes evaporation by direct contact with the rotating body 54, heat transfer from the resin pellets having increased temperature, or contact with the atmosphere having increased temperature. Therefore, the resin pellets can be dried early and highly. Since the humidity of the atmosphere in the inner space 43 and the outer space 44 becomes higher due to the evaporation of moisture, the air in the dehydration dryer is brought outside through the exhaust duct 24 connected to the annular space 42 by the exhaust fan. It is preferable to discharge.
[0025]
The rotating body 54 is provided with a temperature sensor 65 for controlling the temperature . First, the temperature of the rotating body 54 is detected by the temperature sensor 65. Temperature signal detected rotational body 54 is Eject through the remote sensor 67, and the desired temperature set by the detected temperature and the temperature setting device 66 are compared. Their to, so that the temperature of the rotating body 54 becomes equal to the set temperature, the energization of the induction coil 61 is on-off control, or is PID controlled. In this way, the heating temperature of the rotating body 54 is controlled. In that case, multiple classification (e.g. upper portion, middle portion, the upper and lower sections, such as the lower portion) in the axial direction the rotational body 54 is divided into, as well as division also induction coil into a plurality zones Correspondingly, the temperature sensor 65 is also provided with a plurality (65a, 65b, 65c) so as to detect the temperature of each section, and different temperatures are set in the plurality of temperature setting devices (66a, 66b, 66c), for example, The temperature of the rotating body 54 can be controlled so that the temperature in the upper section becomes higher . When such temperature control, it becomes possible humidity of the centrifugal dewatering dryers 50 to cope with the increased as above due to the evaporation of moisture from resin pellets, centrifugation dehydration of vertical structure Optimal temperature control for the dryer 50 can be performed.
Since there is a time delay between the temperature change of the induction coil 61 and the temperature of the rotary body 55, the temperature of the induction coil 61 is directly detected to prevent damage to the induction coil 61 itself. together, it is also possible to achieve further accurate control of the atmospheric temperature in the inner space 43.
[0026]
【The invention's effect】
As is apparent from the above description, according to the present invention, the resin pellets are agitated by the plurality of rotating blades attached to the outer periphery of the rotating body, so that the water adhering to the resin pellets is subjected to centrifugal force through the cylindrical screen. It is dehydrated by the action of. On the other hand, eddy currents are induced in the rotating body by induction heating means to heat the rotating body and increase the temperature of the rotating body and the ambient temperature around it, so that it remains attached to the resin pellet without being dehydrated. Moisture evaporation is promoted. As described above, the centrifugal dehydration dryer according to the present invention is configured not only to dehydrate by shaking off moisture with centrifugal force, but also to evaporate the moisture attached to the resin pellets by heat generated inside the centrifugal dehydration dryer. As a result, the drying efficiency of the pellets can be increased, and the drying capacity of the centrifugal dehydration dryer can be improved without extensive modification of the apparatus. Furthermore, since the removal of moisture from the resin pellets is ensured, the reliability of the resin pellets as a product is improved, and it is not necessary to install a separate drying device, so that the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a centrifugal dewatering dryer for resin pellets according to the present invention, with a part thereof broken away.
FIG. 2 is a cross-sectional view taken along line AA of the centrifugal dewatering dryer for resin pellets shown in FIG.
FIG. 3 is a schematic view showing an underwater cut pellet manufacturing apparatus to which a centrifugal dewatering dryer for resin pellets according to the present invention is applied.
FIG. 4 is a longitudinal sectional view showing an example of a conventional centrifugal dehydration dryer for resin pellets.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Underwater cut type pellet manufacturing apparatus 2 Kneading extruder 10 Cooling water tank 14 Dehydrator 25 Vibration sieving machine 39 Rotary blade 40 Cylindrical screen 43 Inner space 50 Centrifugal dehydration dryer 51 for resin pellets Fixed shaft 54 Rotating body 55 Rotation Body 60 Iron core 61 Induction coil (Induction heating means)
62 Clearance 63 Power supply wire 65 (65a, 65b, 65c) Temperature sensor 66 (66a, 66b, 66c) Temperature setter

Claims (4)

A rotating body in which a plurality of rotating blades are attached to the outer periphery to scrape the resin pellets to which moisture has adhered, and is disposed outside the rotating body, allowing the passage of the moisture but preventing the passage of the resin pellets. comprising a cylindrical screen, and a induction heating means for directly heating the rotary body by inducing eddy currents in the rotating body,
Heating of the rotating body by the induction heating means is controlled based on a detected temperature detected by a temperature sensor provided on the rotating body and a set temperature set by a temperature setting device. A centrifugal dewatering dryer for resin pellets. The rotating body has a rotating body in which the internal hollow, wherein said induction heating means is an induction coil disposed inside the rotating body, the centrifuge resin pellets according to claim 1, wherein Dehydration dryer. The rotating body is disposed around a fixed shaft so as to be concentric with the fixed shaft and rotatably, and the induction coil is slightly in contact with the inner peripheral surface of the rotating body around the iron core attached to the fixed shaft. optionally wound in a state in which a gap, that the induction coil, characterized in that it is adapted current is supplied through a power supply wire disposed on the fixed shaft, resin pellets according to claim 2, wherein Centrifugal dehydration dryer. The temperature sensor is provided for each section obtained by dividing the rotating body into a plurality of parts in the axial direction, and the set temperature is given for each section of the rotating body. The resin according to any one of claims 1 to 3 , wherein heating control is performed for each of the sections based on the detected temperature and the set temperature corresponding to the section. Centrifugal dehydration dryer for pellets.

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